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Financial Data Modelling

Section 4 of 9

Double-entry bookkeeping implemented in SQL, immutable event sourcing, ACID transactions at scale, DynamoDB single-table design, and zero-downtime schema migrations

3 hoursadvanced
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Key Takeaways

  • Every financial transaction requires two ledger entries (debit + credit) — the balance must always sum to zero
  • Financial ledgers are append-only — never UPDATE or DELETE transaction rows, only INSERT
  • SELECT FOR UPDATE and optimistic locking are the two tools for preventing concurrent balance corruption
  • DynamoDB single-table design with conditional writes enables idempotent payment records without transactions
  • Expand-contract migration pattern allows zero-downtime schema changes on high-throughput financial tables

📝Personal Notes

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