DB Olympics

Queries · q209 · Chief Executive Officer · week 2, night 1

Merchant refund-rate spike check, Q4 2025 vs 2025 baseline

“Is the Q4 2025 refund-rate increase concentrated in a handful of merchants, or spread broadly across the merchant base?”

Manager · asked the questionMaren OkaforChief Executive Officer. Joined two weeks ago from a European payments company. Board meeting at the end of January.
Analyst · planned the reportHannah BrooksMethodical: starts with an overview, then drills into whatever looks unusual.
Engineer · wrote the SQLBeaWrites SQL the way the company's BI tool generates it: verbose fully qualified aliases (t0, t1, ...), a subquery per measure joined back on the grain keys, COALESCE everywhere.

Fictional people at a fictional company, each played by a language-model agent. Who they are and what they are told

  1. A business event lands on the Chief Executive Officer's desk

    Week 2; shared with Tobias Lindqvist, Chief Financial Officer

    The board meets at the end of January and wants a clear view of unit economics: per merchant, vertical and country, what Tidewick earns and what it costs us to serve them. Which merchants are worth growing, and which cost more than they bring?

  2. Maren Okafor writes to Hannah Brooks

    The manager, at the start of week 2

    Subject: Great first week — here's where I want to go next

    Hannah,

    This was exactly the kind of grounding I needed — thank you. A few things surprised me and one big new ask from the board that I need us to lead together with Tobias.

    What surprised me / needs explaining:

    • Your fee-revenue figure (€53k trailing twelve months) and Tobias's (€93.6k for calendar 2025) don't match, and neither does your "72% from top 5, stable" concentration story line up cleanly with his "65% from top 10, declining as we add merchants." Before this goes near the board I need these reconciled into one number and one trend — I don't want finance and analytics telling different stories about the same business.
    • The refund story looks more nuanced than "refunds are creeping up broadly." Tobias's team says apparel's ~20% refund rate is just normal for the category, and the real spike this quarter came from a few smaller non-apparel merchants. I'd like your root-cause work to confirm or correct that before we flag it as a trend versus a one-off.
    • Operations found that delivery performance is almost entirely a carrier issue, not a merchant or warehouse issue — the same merchant looks great on one carrier and bad on another, and one carrier partner has clearly been underperforming since November. That changes how I think about "merchant health" — some of what looks like a merchant problem may really be a carrier problem.

    The new board ask — unit economics by merchant, vertical and country:

    The board wants to know, plainly, what we earn from serving each merchant/vertical/country and what it costs us — so we can say which parts of the business are worth leaning into and which are quietly expensive. This is bigger than one report, so here's what I think it needs, and I want you and Tobias to scope it jointly this week rather than me prescribing the method:

    • On the earnings side, we seem to have good data (processing fees, volume). Platform-plan fees are apparently missing from the warehouse — Tobias, can your team supply that separately so we're not missing a real revenue line?
    • On the cost side, I don't think we've ever assembled this: fulfillment/carrier cost, refund and return handling, support load, and the engineering reliability issues (webhook failures, the cart-reminder bug) that generate extra support tickets. Some of this may not be cleanly attributable per merchant in the data — I want an honest read on what's knowable now versus what needs to be modeled or estimated.
    • The deliverable I need by month-end: a short ranked view of which merchants/verticals/countries are clearly profitable to grow, which are marginal, and which likely cost more to serve than they return — even if the first pass is directional rather than precise.

    My questions for this week:

    1. Can you and Tobias reconcile the revenue and concentration numbers into a single, agreed figure and trend I can quote to the board without contradiction?
    2. What would it take to build even a rough cost-to-serve picture per merchant/vertical/country — and what's your honest confidence in it, given the data gaps you've already flagged (platform fees, refund-to-payout matching, carrier cost attribution)?
    3. On refunds — is the increase really concentrated in a few merchants/verticals as Tobias's team suggests, or is it broader? I want to know whether this is a few accounts to manage or a trend to worry about.
    4. Separately, flag for me which of our top accounts (like Castell Fasteners, with its traffic drop and unpaid invoices) look at risk — I want a short "accounts to watch" list alongside the unit economics work, not buried inside it.

    Let's talk briefly before you lock in this week's requests so we spend the slots on the unit economics scoping rather than re-running what we already mostly know.

    Thanks, Maren

    A note from the Chief Financial Officer, Tobias Lindqvist

    Note to Hannah Brooks

    Hannah — a few things from the finance side as you scope the board unit-economics piece:

    1. What does each merchant actually net us, after processing costs? We only see the economics clearly once payouts are broken into gross, fee, and net — a merchant with huge volume but thin margin on our fee side could look better on revenue than it really is on contribution.
    2. How exposed are we on currency? We earn and hold balances in many merchant currencies against a EUR view for the board — I want to know where FX swings could meaningfully move the 2025 numbers or the 2026 budget.
    3. Who's slow to pay us, and where? For the B2B wholesalers especially, I'd like a sense of outstanding receivables and how long they're taking to settle — that's a cost of serving them that doesn't show up in the headline revenue.

    If there's room, a rough read on how refund patterns differ by vertical or country would help round out the "which merchants are worth growing" question.

    Happy to talk through before Friday's memo.

    — Tobias

  3. Hannah Brooks plans the night

    The analyst · week 2, night 1, request 2 of 3

    Top priority tonight is giving Maren and Tobias's team concrete evidence to reconcile the revenue numbers, rather than just re-asserting my figure. I've cross-checked internally: my €53,186 fee revenue / €1,991,449 gross volume for 2025 is consistent across two independent reports (merchant-level and corrected vertical-level) built with an explicit, auditable method (status='paid', exact-date EUR conversion). Notably, Kofi's €93,583 figure is almost exactly 1.76x mine — the same ratio as the original buggy vertical report I caught and fixed in week 1 — which strongly suggests his team's query has a similar join fan-out (likely against exchange_rates or a one-to-many table), not a genuine methodology difference. A clean currency-level breakdown tonight will (a) give me hard evidence to bring to a joint session with Tobias's team, and (b) double as the FX-exposure view Tobias asked for. I'm also using tonight's other two slots on items Maren explicitly wants resolved this week outside the bigger unit-economics scoping: testing whether the refund uptick is concentrated (per Kofi's claim) or broad, and building the "accounts to watch" risk snapshot (which also answers Tobias's receivables-aging question). I'm deliberately not starting the cost-to-serve/unit-economics build yet — that needs a design conversation with Tobias before I spend slots on it.

    Merchant refund-rate spike check, Q4 2025 vs 2025 baseline
    Question
    Is the Q4 2025 refund-rate increase concentrated in a handful of merchants, or spread broadly across the merchant base?
    One row per
    merchant (tenant)
    Columns
    • merchant name
    • vertical
    • refund rate Q4 2025 (%)
    • refund rate Q1-Q3 2025 baseline (%)
    • change vs own baseline (percentage points)
    • refund amount Q4 2025 (EUR)
    • order count Q4 2025
  4. Bea writes the SQL

    The engineer · 1 dry run on the empty schema, then the submission

    Dry run 1 · STATUS: COMPILES (dry run on the empty schema, no data read)
    WITH t1 AS (
      SELECT
        t10.tenant_id AS tenant_id,
        SUM(t10.amount / t11.rate) AS captured_eur_q4,
        COUNT(DISTINCT t10.order_id) AS order_count_q4
      FROM payments AS t10
      JOIN exchange_rates AS t11
        ON t11.base_code = 'EUR'
       AND t11.quote_code = t10.currency_code
       AND t11.as_of = CAST(t10.captured_at AS date)
      WHERE t10.status IN ('captured', 'partially_refunded', 'refunded')
        AND t10.captured_at >= DATE '2025-10-01'
        AND t10.captured_at < DATE '2026-01-01'
      GROUP BY t10.tenant_id
    ),
    t2 AS (
      SELECT
        t20.tenant_id AS tenant_id,
        SUM(t20.amount / t21.rate) AS captured_eur_baseline
      FROM payments AS t20
      JOIN exchange_rates AS t21
        ON t21.base_code = 'EUR'
       AND t21.quote_code = t20.currency_code
       AND t21.as_of = CAST(t20.captured_at AS date)
      WHERE t20.status IN ('captured', 'partially_refunded', 'refunded')
        AND t20.captured_at >= DATE '2025-01-01'
        AND t20.captured_at < DATE '2025-10-01'
      GROUP BY t20.tenant_id
    ),
    t3 AS (
      SELECT
        t30.tenant_id AS tenant_id,
        SUM(t30.amount / t31.rate) AS refund_eur_q4
      FROM payment_refunds AS t30
      JOIN exchange_rates AS t31
        ON t31.base_code = 'EUR'
       AND t31.quote_code = t30.currency_code
       AND t31.as_of = CAST(t30.processed_at AS date)
      WHERE t30.status = 'succeeded'
        AND t30.processed_at >= DATE '2025-10-01'
        AND t30.processed_at < DATE '2026-01-01'
      GROUP BY t30.tenant_id
    ),
    t4 AS (
      SELECT
        t40.tenant_id AS tenant_id,
        SUM(t40.amount / t41.rate) AS refund_eur_baseline
      FROM payment_refunds AS t40
      JOIN exchange_rates AS t41
        ON t41.base_code = 'EUR'
       AND t41.quote_code = t40.currency_code
       AND t41.as_of = CAST(t40.processed_at AS date)
      WHERE t40.status = 'succeeded'
        AND t40.processed_at >= DATE '2025-01-01'
        AND t40.processed_at < DATE '2025-10-01'
      GROUP BY t40.tenant_id
    )
    SELECT
      t0.name AS merchant_name,
      t0.industry AS vertical,
      ROUND(100.0 * COALESCE(t3.refund_eur_q4, 0) / NULLIF(t1.captured_eur_q4, 0), 2) AS refund_rate_q4_pct,
      ROUND(100.0 * COALESCE(t4.refund_eur_baseline, 0) / NULLIF(t2.captured_eur_baseline, 0), 2) AS refund_rate_baseline_pct,
      ROUND(
        (100.0 * COALESCE(t3.refund_eur_q4, 0) / NULLIF(t1.captured_eur_q4, 0))
        - (100.0 * COALESCE(t4.refund_eur_baseline, 0) / NULLIF(t2.captured_eur_baseline, 0))
      , 2) AS change_vs_baseline_pp,
      ROUND(COALESCE(t3.refund_eur_q4, 0), 2) AS refund_amount_q4_eur,
      t1.order_count_q4 AS order_count_q4
    FROM tenants AS t0
    JOIN t1 ON t1.tenant_id = t0.id
    LEFT JOIN t2 ON t2.tenant_id = t0.id
    LEFT JOIN t3 ON t3.tenant_id = t0.id
    LEFT JOIN t4 ON t4.tenant_id = t0.id
    WHERE t1.order_count_q4 >= 10
    ORDER BY change_vs_baseline_pp DESC NULLS LAST, refund_amount_q4_eur DESC, t0.id ASC

    “Query compiles cleanly. Submitting now.”

    Submitted · the SQL of the last dry run, unchanged · Submitted to tonight's batch. Your work on this request is done.

    “Submitted. Summary of approach: - Grain: one row per tenant/merchant, filtered to those with ≥10 qualifying orders in Q4 2025. - Numerators/denominators: computed as four separate CTEs (Q4 captured EUR + order count, Q1–Q3 captured EUR, Q4 refund EUR, Q1–Q3 refund EUR), each converting local currency to EUR via exchange_rates joined on as_of = cast(date, …). - Rates & change: refund_rate_q4_pct, refund_rate_baseline_pct, and change_vs_baseline_pp (the sort key, descending, tie-broken by Q4 refund EUR then tenant id for determinism). - Deviation noted to the analyst: used the tenant_id columns already present on payments/payment_refunds directly rather than routing through orders, since both tables carry it natively — same attribution, simpler join. Baseline-less merchants get a null rate/change and sort last.”

  5. The report comes back overnight

    As Hannah Brooks saw it, from the small dataset the agents worked on

    merchant_name          | vertical                  | refund_rate_q4_pct | refund_rate_baseline_pct | change_vs_baseline_pp | refund_amount_q4_eur | order_count_q4
    -----------------------+---------------------------+--------------------+--------------------------+-----------------------+----------------------+---------------
    Fell & Fjell           | Sports & Outdoor          |              83.02 |                     3.38 |                 79.64 |              4888.59 |             17
    Bytefield              | Consumer Electronics      |              52.58 |                      0.0 |                 52.58 |              4487.99 |             11
    Brick & Bobbin         | Apparel & Footwear        |              50.06 |                    32.79 |                 17.27 |               612.92 |             10
    Lamplight Living       | Home & Living             |              20.44 |                      6.9 |                 13.54 |               494.36 |             20
    Saffron & Sage         | Beauty                    |              11.76 |                     3.56 |                  8.21 |               554.55 |             33
    Feather & Fin          | Pet Supplies              |               8.76 |                     1.88 |                  6.88 |               290.54 |             48
    Cinder Peak Sports Co. | Sports & Outdoor          |              18.23 |                    11.42 |                  6.81 |              6920.67 |            105
    Willow & Wren          | Home & Living             |              16.43 |                    11.29 |                  5.14 |               929.47 |             33
    Purrfect Pantry        | Pet Supplies              |               6.62 |                     2.38 |                  4.24 |                54.47 |             17
    Rosehip Lab            | Beauty                    |               3.17 |                      0.0 |                  3.17 |                44.48 |             16
    Hus & Hem              | Home & Living             |               9.48 |                     6.81 |                  2.66 |                172.0 |             15
    Grind Collective       | Food & Coffee             |               3.16 |                     0.74 |                  2.43 |               367.54 |            166
    Petalcourt Beauty      | Beauty                    |               8.46 |                     6.83 |                  1.63 |              1775.91 |            250
    The Balm Room          | Beauty                    |               6.49 |                     5.16 |                  1.33 |               276.16 |             32
    Oakhurst Tailoring     | Apparel & Footwear        |              14.91 |                    13.66 |                  1.25 |              2106.35 |             83
    Nordic Bloom Cosmetics | Beauty                    |               8.67 |                     7.62 |                  1.05 |               468.27 |             45
    Castell Fasteners      | Industrial Supplies (B2B) |               0.86 |                     0.23 |                  0.63 |               885.79 |             47
    Roast Republic         | Food & Coffee             |                0.0 |                      0.0 |                   0.0 |                  0.0 |             21
    Deskline Supplies      | Office Supplies (B2B)     |                0.0 |                     0.37 |                 -0.37 |                  0.0 |             20
    Paperplane Press       | Books & Stationery        |               2.35 |                     3.11 |                 -0.77 |                16.07 |             15
    Kibblewick             | Pet Supplies              |                0.3 |                     1.14 |                 -0.84 |                28.98 |            100
    Tiny Atelier           | Home & Living             |               5.86 |                     7.44 |                 -1.58 |                79.96 |             10
    Honeycomb Larder       | Food & Coffee             |               0.06 |                     1.81 |                 -1.75 |                 6.21 |             91
    Marrowby & Vane        | Apparel & Footwear        |              21.07 |                    23.13 |                 -2.06 |             24695.74 |            642
    Coastline Interiors    | Home & Living             |               6.07 |                     8.39 |                 -2.31 |               548.01 |             67
    Tail Wag Supply        | Pet Supplies              |                0.0 |                     2.37 |                 -2.37 |                  0.0 |             29
    Cragsley Outfitters    | Apparel & Footwear        |              22.56 |                    25.05 |                  -2.5 |             70042.32 |           1413
    Fennel & Flint         | Home & Living             |               4.19 |                     7.45 |                 -3.26 |              1288.42 |            173
    Fjordline Wear         | Apparel & Footwear        |               25.8 |                    29.07 |                 -3.27 |                851.8 |             24
    Juniper Apothecary     | Beauty                    |                2.5 |                     6.78 |                 -4.28 |               153.65 |             55
    Folio & Fern           | Books & Stationery        |               2.39 |                     7.04 |                 -4.65 |                24.39 |             22
    Stoneware Studio       | Home & Living             |                0.0 |                     5.75 |                 -5.75 |                  0.0 |             12
    Kayak Corner           | Sports & Outdoor          |               3.36 |                     9.76 |                 -6.39 |               259.69 |             22
    Thistlecombe           | Apparel & Footwear        |              15.63 |                    23.48 |                 -7.84 |              1029.61 |             42
    OfficeHub Nordic       | Office Supplies (B2B)     |                0.0 |                     9.16 |                 -9.16 |                  0.0 |             55
    Velvet Ash             | Apparel & Footwear        |              15.62 |                    32.26 |                -16.64 |              1784.84 |             51
    (36 rows)
  6. What came of it

    The memo and the queries that followed; links found by title, so inferred

    Later queries that build on this report:

  7. It becomes benchmark query q209

    Changed only where the benchmark needs the same result on every system

    • numericsdocs/NUMERICS.md: rounding removed; results keep full precision
    • numericsdocs/NUMERICS.md: x / exchange rate cast to NUMERIC(18,6) (4×)
    • determinismthe standard leaves the place of NULLs in a sort to the implementation: NULLS LAST ascending, NULLS FIRST descending, as in the reference results (2×)
    The benchmark text, against the submitted SQL
    WITH t1 AS (  SELECT    t10.tenant_id AS tenant_id,    SUM(t10.amount / t11.rate) AS captured_eur_q4,    SUM(CAST(t10.amount / t11.rate AS NUMERIC(18,6))) AS captured_eur_q4,    COUNT(DISTINCT t10.order_id) AS order_count_q4  FROM payments AS t10  JOIN exchange_rates AS t11    ON t11.base_code = 'EUR'   AND t11.quote_code = t10.currency_code   AND t11.as_of = CAST(t10.captured_at AS date)  WHERE t10.status IN ('captured', 'partially_refunded', 'refunded')    AND t10.captured_at >= DATE '2025-10-01'    AND t10.captured_at < DATE '2026-01-01'  GROUP BY t10.tenant_id),t2 AS (  SELECT    t20.tenant_id AS tenant_id,    SUM(t20.amount / t21.rate) AS captured_eur_baseline    SUM(CAST(t20.amount / t21.rate AS NUMERIC(18,6))) AS captured_eur_baseline  FROM payments AS t20  JOIN exchange_rates AS t21    ON t21.base_code = 'EUR'   AND t21.quote_code = t20.currency_code   AND t21.as_of = CAST(t20.captured_at AS date)  WHERE t20.status IN ('captured', 'partially_refunded', 'refunded')    AND t20.captured_at >= DATE '2025-01-01'    AND t20.captured_at < DATE '2025-10-01'  GROUP BY t20.tenant_id),t3 AS (  SELECT    t30.tenant_id AS tenant_id,    SUM(t30.amount / t31.rate) AS refund_eur_q4    SUM(CAST(t30.amount / t31.rate AS NUMERIC(18,6))) AS refund_eur_q4  FROM payment_refunds AS t30  JOIN exchange_rates AS t31    ON t31.base_code = 'EUR'   AND t31.quote_code = t30.currency_code   AND t31.as_of = CAST(t30.processed_at AS date)  WHERE t30.status = 'succeeded'    AND t30.processed_at >= DATE '2025-10-01'    AND t30.processed_at < DATE '2026-01-01'  GROUP BY t30.tenant_id),t4 AS (  SELECT    t40.tenant_id AS tenant_id,    SUM(t40.amount / t41.rate) AS refund_eur_baseline    SUM(CAST(t40.amount / t41.rate AS NUMERIC(18,6))) AS refund_eur_baseline  FROM payment_refunds AS t40  JOIN exchange_rates AS t41    ON t41.base_code = 'EUR'   AND t41.quote_code = t40.currency_code   AND t41.as_of = CAST(t40.processed_at AS date)  WHERE t40.status = 'succeeded'    AND t40.processed_at >= DATE '2025-01-01'    AND t40.processed_at < DATE '2025-10-01'  GROUP BY t40.tenant_id)SELECT  t0.name AS merchant_name,  t0.industry AS vertical,  ROUND(100.0 * COALESCE(t3.refund_eur_q4, 0) / NULLIF(t1.captured_eur_q4, 0), 2) AS refund_rate_q4_pct,  ROUND(100.0 * COALESCE(t4.refund_eur_baseline, 0) / NULLIF(t2.captured_eur_baseline, 0), 2) AS refund_rate_baseline_pct,  ROUND(    (100.0 * COALESCE(t3.refund_eur_q4, 0) / NULLIF(t1.captured_eur_q4, 0))    - (100.0 * COALESCE(t4.refund_eur_baseline, 0) / NULLIF(t2.captured_eur_baseline, 0))  , 2) AS change_vs_baseline_pp,  ROUND(COALESCE(t3.refund_eur_q4, 0), 2) AS refund_amount_q4_eur,  100.0 * COALESCE(t3.refund_eur_q4, 0) / NULLIF(t1.captured_eur_q4, 0) AS refund_rate_q4_pct,  100.0 * COALESCE(t4.refund_eur_baseline, 0) / NULLIF(t2.captured_eur_baseline, 0) AS refund_rate_baseline_pct,  (100.0 * COALESCE(t3.refund_eur_q4, 0) / NULLIF(t1.captured_eur_q4, 0))  - (100.0 * COALESCE(t4.refund_eur_baseline, 0) / NULLIF(t2.captured_eur_baseline, 0)) AS change_vs_baseline_pp,  COALESCE(t3.refund_eur_q4, 0) AS refund_amount_q4_eur,  t1.order_count_q4 AS order_count_q4FROM tenants AS t0JOIN t1 ON t1.tenant_id = t0.idLEFT JOIN t2 ON t2.tenant_id = t0.idLEFT JOIN t3 ON t3.tenant_id = t0.idLEFT JOIN t4 ON t4.tenant_id = t0.idWHERE t1.order_count_q4 >= 10ORDER BY change_vs_baseline_pp DESC NULLS LAST, refund_amount_q4_eur DESC, t0.id ASCORDER BY change_vs_baseline_pp DESC NULLS LAST, refund_amount_q4_eur DESC NULLS FIRST, t0.id ASC NULLS LAST
    WITH t1 AS (
      SELECT
        t10.tenant_id AS tenant_id,
        SUM(CAST(t10.amount / t11.rate AS NUMERIC(18,6))) AS captured_eur_q4,
        COUNT(DISTINCT t10.order_id) AS order_count_q4
      FROM payments AS t10
      JOIN exchange_rates AS t11
        ON t11.base_code = 'EUR'
       AND t11.quote_code = t10.currency_code
       AND t11.as_of = CAST(t10.captured_at AS date)
      WHERE t10.status IN ('captured', 'partially_refunded', 'refunded')
        AND t10.captured_at >= DATE '2025-10-01'
        AND t10.captured_at < DATE '2026-01-01'
      GROUP BY t10.tenant_id
    ),
    t2 AS (
      SELECT
        t20.tenant_id AS tenant_id,
        SUM(CAST(t20.amount / t21.rate AS NUMERIC(18,6))) AS captured_eur_baseline
      FROM payments AS t20
      JOIN exchange_rates AS t21
        ON t21.base_code = 'EUR'
       AND t21.quote_code = t20.currency_code
       AND t21.as_of = CAST(t20.captured_at AS date)
      WHERE t20.status IN ('captured', 'partially_refunded', 'refunded')
        AND t20.captured_at >= DATE '2025-01-01'
        AND t20.captured_at < DATE '2025-10-01'
      GROUP BY t20.tenant_id
    ),
    t3 AS (
      SELECT
        t30.tenant_id AS tenant_id,
        SUM(CAST(t30.amount / t31.rate AS NUMERIC(18,6))) AS refund_eur_q4
      FROM payment_refunds AS t30
      JOIN exchange_rates AS t31
        ON t31.base_code = 'EUR'
       AND t31.quote_code = t30.currency_code
       AND t31.as_of = CAST(t30.processed_at AS date)
      WHERE t30.status = 'succeeded'
        AND t30.processed_at >= DATE '2025-10-01'
        AND t30.processed_at < DATE '2026-01-01'
      GROUP BY t30.tenant_id
    ),
    t4 AS (
      SELECT
        t40.tenant_id AS tenant_id,
        SUM(CAST(t40.amount / t41.rate AS NUMERIC(18,6))) AS refund_eur_baseline
      FROM payment_refunds AS t40
      JOIN exchange_rates AS t41
        ON t41.base_code = 'EUR'
       AND t41.quote_code = t40.currency_code
       AND t41.as_of = CAST(t40.processed_at AS date)
      WHERE t40.status = 'succeeded'
        AND t40.processed_at >= DATE '2025-01-01'
        AND t40.processed_at < DATE '2025-10-01'
      GROUP BY t40.tenant_id
    )
    SELECT
      t0.name AS merchant_name,
      t0.industry AS vertical,
      100.0 * COALESCE(t3.refund_eur_q4, 0) / NULLIF(t1.captured_eur_q4, 0) AS refund_rate_q4_pct,
      100.0 * COALESCE(t4.refund_eur_baseline, 0) / NULLIF(t2.captured_eur_baseline, 0) AS refund_rate_baseline_pct,
      (100.0 * COALESCE(t3.refund_eur_q4, 0) / NULLIF(t1.captured_eur_q4, 0))
      - (100.0 * COALESCE(t4.refund_eur_baseline, 0) / NULLIF(t2.captured_eur_baseline, 0)) AS change_vs_baseline_pp,
      COALESCE(t3.refund_eur_q4, 0) AS refund_amount_q4_eur,
      t1.order_count_q4 AS order_count_q4
    FROM tenants AS t0
    JOIN t1 ON t1.tenant_id = t0.id
    LEFT JOIN t2 ON t2.tenant_id = t0.id
    LEFT JOIN t3 ON t3.tenant_id = t0.id
    LEFT JOIN t4 ON t4.tenant_id = t0.id
    WHERE t1.order_count_q4 >= 10
    ORDER BY change_vs_baseline_pp DESC NULLS LAST, refund_amount_q4_eur DESC NULLS FIRST, t0.id ASC NULLS LAST
    10 ms100 ms1 sHyper116 msDuckDB51.6 msGizmoSQL58.9 msclickhouse_brew327 msFirebolterrorDataFusionerrorClickHouseerror
    • Firebolt{ "errors": [ { "description": "Line 4, Column 25: Operations between decimals with different precision and scale is not supported at the moment. Explicitly cast one of the decimals to other decimal precision and scale." } ], "query": { "query_id": "032f9988-8462-4549-bad4-128363cf9701", "query_labe
    • DataFusionArrow error: Invalid argument error: Invalid comparison operation: Decimal128(38, 6) == Decimal128(28, 6)
    • ClickHouseCode: 69. DB::Exception: Decimal result's scale is less than argument's one: while executing function divide on arguments __table3.amount Decimal(14, 4) Decimal64(size = 0), __table4.rate Decimal(12, 6) Decimal64(size = 0). (ARGUMENT_OUT_OF_BOUND)
  8. Everything, as recorded

    The agents' own records, as the role play wrote them; only the personal data of the person who ran it is redacted

    Bea's whole session, 7 turns
    • The request, as Bea received it
      Report request from Hannah Brooks (analyst for the Chief Executive Officer):
      
      Title: Merchant refund-rate spike check, Q4 2025 vs 2025 baseline
      Question: Is the Q4 2025 refund-rate increase concentrated in a handful of merchants, or spread broadly across the merchant base?
      Grain: one row per merchant (tenant)
      Columns:
      - merchant name
      - vertical
      - refund rate Q4 2025 (%)
      - refund rate Q1-Q3 2025 baseline (%)
      - change vs own baseline (percentage points)
      - refund amount Q4 2025 (EUR)
      - order count Q4 2025
      Details: Source: payment_refunds (status='succeeded', processed_at in quarter, amount converted to EUR via exchange_rates as_of processed_at date) as the numerator, divided by payments (status in 'captured','partially_refunded','refunded', captured_at in quarter, amount converted to EUR via exchange_rates as_of captured_at date) as the denominator, both joined to orders->tenants (or directly via payments.order_id->orders.tenant_id) to attribute to a merchant. Compute refund rate = 100 * refund EUR / captured payment EUR, once for Q4 2025 (2025-10-01 to 2026-01-01) and once pooled across Q1-Q3 2025 (2025-01-01 to 2025-10-01) as each merchant's own baseline. 'Change vs own baseline' lets us separate merchants with a structurally high rate (e.g. apparel, reportedly ~20% normally) from merchants whose rate genuinely jumped in Q4. Include only merchants with at least 10 orders in Q4 2025 to avoid noise from tiny volumes. Order by change vs own baseline descending (biggest jumps first), tie-break by refund amount Q4 2025 descending. Note total merchant count returned.
      
      Check your query with the warehouse's dry_run tool, then hand it in with submit.
    • Bea calls dry_run
      WITH t1 AS (
        SELECT
          t10.tenant_id AS tenant_id,
          SUM(t10.amount / t11.rate) AS captured_eur_q4,
          COUNT(DISTINCT t10.order_id) AS order_count_q4
        FROM payments AS t10
        JOIN exchange_rates AS t11
          ON t11.base_code = 'EUR'
         AND t11.quote_code = t10.currency_code
         AND t11.as_of = CAST(t10.captured_at AS date)
        WHERE t10.status IN ('captured', 'partially_refunded', 'refunded')
          AND t10.captured_at >= DATE '2025-10-01'
          AND t10.captured_at < DATE '2026-01-01'
        GROUP BY t10.tenant_id
      ),
      t2 AS (
        SELECT
          t20.tenant_id AS tenant_id,
          SUM(t20.amount / t21.rate) AS captured_eur_baseline
        FROM payments AS t20
        JOIN exchange_rates AS t21
          ON t21.base_code = 'EUR'
         AND t21.quote_code = t20.currency_code
         AND t21.as_of = CAST(t20.captured_at AS date)
        WHERE t20.status IN ('captured', 'partially_refunded', 'refunded')
          AND t20.captured_at >= DATE '2025-01-01'
          AND t20.captured_at < DATE '2025-10-01'
        GROUP BY t20.tenant_id
      ),
      t3 AS (
        SELECT
          t30.tenant_id AS tenant_id,
          SUM(t30.amount / t31.rate) AS refund_eur_q4
        FROM payment_refunds AS t30
        JOIN exchange_rates AS t31
          ON t31.base_code = 'EUR'
         AND t31.quote_code = t30.currency_code
         AND t31.as_of = CAST(t30.processed_at AS date)
        WHERE t30.status = 'succeeded'
          AND t30.processed_at >= DATE '2025-10-01'
          AND t30.processed_at < DATE '2026-01-01'
        GROUP BY t30.tenant_id
      ),
      t4 AS (
        SELECT
          t40.tenant_id AS tenant_id,
          SUM(t40.amount / t41.rate) AS refund_eur_baseline
        FROM payment_refunds AS t40
        JOIN exchange_rates AS t41
          ON t41.base_code = 'EUR'
         AND t41.quote_code = t40.currency_code
         AND t41.as_of = CAST(t40.processed_at AS date)
        WHERE t40.status = 'succeeded'
          AND t40.processed_at >= DATE '2025-01-01'
          AND t40.processed_at < DATE '2025-10-01'
        GROUP BY t40.tenant_id
      )
      SELECT
        t0.name AS merchant_name,
        t0.industry AS vertical,
        ROUND(100.0 * COALESCE(t3.refund_eur_q4, 0) / NULLIF(t1.captured_eur_q4, 0), 2) AS refund_rate_q4_pct,
        ROUND(100.0 * COALESCE(t4.refund_eur_baseline, 0) / NULLIF(t2.captured_eur_baseline, 0), 2) AS refund_rate_baseline_pct,
        ROUND(
          (100.0 * COALESCE(t3.refund_eur_q4, 0) / NULLIF(t1.captured_eur_q4, 0))
          - (100.0 * COALESCE(t4.refund_eur_baseline, 0) / NULLIF(t2.captured_eur_baseline, 0))
        , 2) AS change_vs_baseline_pp,
        ROUND(COALESCE(t3.refund_eur_q4, 0), 2) AS refund_amount_q4_eur,
        t1.order_count_q4 AS order_count_q4
      FROM tenants AS t0
      JOIN t1 ON t1.tenant_id = t0.id
      LEFT JOIN t2 ON t2.tenant_id = t0.id
      LEFT JOIN t3 ON t3.tenant_id = t0.id
      LEFT JOIN t4 ON t4.tenant_id = t0.id
      WHERE t1.order_count_q4 >= 10
      ORDER BY change_vs_baseline_pp DESC NULLS LAST, refund_amount_q4_eur DESC, t0.id ASC
    • The warehouse answers
      STATUS: COMPILES (dry run on the empty schema, no data read)
      COLUMNS: merchant_name, vertical, refund_rate_q4_pct, refund_rate_baseline_pct, change_vs_baseline_pp, refund_amount_q4_eur, order_count_q4
    • BeaQuery compiles cleanly. Submitting now.
    • Bea calls submit
      WITH t1 AS (
        SELECT
          t10.tenant_id AS tenant_id,
          SUM(t10.amount / t11.rate) AS captured_eur_q4,
          COUNT(DISTINCT t10.order_id) AS order_count_q4
        FROM payments AS t10
        JOIN exchange_rates AS t11
          ON t11.base_code = 'EUR'
         AND t11.quote_code = t10.currency_code
         AND t11.as_of = CAST(t10.captured_at AS date)
        WHERE t10.status IN ('captured', 'partially_refunded', 'refunded')
          AND t10.captured_at >= DATE '2025-10-01'
          AND t10.captured_at < DATE '2026-01-01'
        GROUP BY t10.tenant_id
      ),
      t2 AS (
        SELECT
          t20.tenant_id AS tenant_id,
          SUM(t20.amount / t21.rate) AS captured_eur_baseline
        FROM payments AS t20
        JOIN exchange_rates AS t21
          ON t21.base_code = 'EUR'
         AND t21.quote_code = t20.currency_code
         AND t21.as_of = CAST(t20.captured_at AS date)
        WHERE t20.status IN ('captured', 'partially_refunded', 'refunded')
          AND t20.captured_at >= DATE '2025-01-01'
          AND t20.captured_at < DATE '2025-10-01'
        GROUP BY t20.tenant_id
      ),
      t3 AS (
        SELECT
          t30.tenant_id AS tenant_id,
          SUM(t30.amount / t31.rate) AS refund_eur_q4
        FROM payment_refunds AS t30
        JOIN exchange_rates AS t31
          ON t31.base_code = 'EUR'
         AND t31.quote_code = t30.currency_code
         AND t31.as_of = CAST(t30.processed_at AS date)
        WHERE t30.status = 'succeeded'
          AND t30.processed_at >= DATE '2025-10-01'
          AND t30.processed_at < DATE '2026-01-01'
        GROUP BY t30.tenant_id
      ),
      t4 AS (
        SELECT
          t40.tenant_id AS tenant_id,
          SUM(t40.amount / t41.rate) AS refund_eur_baseline
        FROM payment_refunds AS t40
        JOIN exchange_rates AS t41
          ON t41.base_code = 'EUR'
         AND t41.quote_code = t40.currency_code
         AND t41.as_of = CAST(t40.processed_at AS date)
        WHERE t40.status = 'succeeded'
          AND t40.processed_at >= DATE '2025-01-01'
          AND t40.processed_at < DATE '2025-10-01'
        GROUP BY t40.tenant_id
      )
      SELECT
        t0.name AS merchant_name,
        t0.industry AS vertical,
        ROUND(100.0 * COALESCE(t3.refund_eur_q4, 0) / NULLIF(t1.captured_eur_q4, 0), 2) AS refund_rate_q4_pct,
        ROUND(100.0 * COALESCE(t4.refund_eur_baseline, 0) / NULLIF(t2.captured_eur_baseline, 0), 2) AS refund_rate_baseline_pct,
        ROUND(
          (100.0 * COALESCE(t3.refund_eur_q4, 0) / NULLIF(t1.captured_eur_q4, 0))
          - (100.0 * COALESCE(t4.refund_eur_baseline, 0) / NULLIF(t2.captured_eur_baseline, 0))
        , 2) AS change_vs_baseline_pp,
        ROUND(COALESCE(t3.refund_eur_q4, 0), 2) AS refund_amount_q4_eur,
        t1.order_count_q4 AS order_count_q4
      FROM tenants AS t0
      JOIN t1 ON t1.tenant_id = t0.id
      LEFT JOIN t2 ON t2.tenant_id = t0.id
      LEFT JOIN t3 ON t3.tenant_id = t0.id
      LEFT JOIN t4 ON t4.tenant_id = t0.id
      WHERE t1.order_count_q4 >= 10
      ORDER BY change_vs_baseline_pp DESC NULLS LAST, refund_amount_q4_eur DESC, t0.id ASC
    • The warehouse answers
      Submitted to tonight's batch. Your work on this request is done.
    • BeaSubmitted. Summary of approach: - **Grain:** one row per tenant/merchant, filtered to those with ≥10 qualifying orders in Q4 2025. - **Numerators/denominators:** computed as four separate CTEs (Q4 captured EUR + order count, Q1–Q3 captured EUR, Q4 refund EUR, Q1–Q3 refund EUR), each converting local currency to EUR via `exchange_rates` joined on `as_of = cast(date, …)`. - **Rates & change:** `refund_rate_q4_pct`, `refund_rate_baseline_pct`, and `change_vs_baseline_pp` (the sort key, descending, tie-broken by Q4 refund EUR then tenant id for determinism). - **Deviation noted to the analyst:** used the `tenant_id` columns already present on `payments`/`payment_refunds` directly rather than routing through `orders`, since both tables carry it natively — same attribution, simpler join. Baseline-less merchants get a null rate/change and sort last.