Fintech Development

Ledger Reconciliation Job Prompt

Design a reconciliation job that compares internal ledger records against a payment processor's records and flags discrepancies for review.

Anselm Fowel / Public collection29 Sept 2026

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The prompt

You are a fintech engineer who owns the reconciliation pipeline at a company processing payments through [PROCESSOR: STRIPE / ADYEN / A BANKING PARTNER], and you've learned that reconciliation bugs hide real money problems for months if the job isn't designed defensively.

My internal ledger lives in [DATABASE] and I receive [SETTLEMENT FILES / API REPORTS / BOTH] from [PROCESSOR NAME] on a [DAILY / HOURLY] basis. Transaction volume is roughly [VOLUME] per day across [CURRENCIES].

First, design the matching key strategy: what field ties an internal transaction to the processor's record (processor transaction ID, idempotency key, or a derived composite), and how you handle records that exist on one side but not the other due to timing (a transaction settled by the processor but not yet reflected internally, or vice versa).

Next, define the categories of discrepancy this job must detect: missing on our side, missing on processor side, amount mismatch, currency mismatch, fee mismatch, and status mismatch (e.g., we show succeeded, processor shows refunded). For each category, specify the exact comparison logic and the tolerance, if any, for timing-related false positives.

Then design how discrepancies are surfaced: a discrepancies table schema with severity levels, an alerting threshold for when discrepancy volume itself indicates a systemic bug rather than isolated timing noise, and a clear escalation path distinguishing discrepancies that require an engineer versus ones that finance can resolve manually.

Finally, write the reconciliation job's core comparison logic in [LANGUAGE/FRAMEWORK] with comments, followed by a test plan covering: a transaction present only internally, one present only externally, an amount off by one cent, a duplicate processor record, and a transaction that reconciles correctly after a delayed settlement, each with expected job behavior.

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