Fintech Payment Flow – Scale-Up

12 min · scale-up · intermediate

Fintech Payment Flow – Scale-Up

Context: 100k transactions/day. Same-region for now. Must remain strongly consistent.

Scale-Up Design

  • DB: Connection pooling, read replicas for balance queries (read-your-writes).
  • Queue: For non-critical side effects (notifications, analytics). Core debit/credit stays synchronous.
  • Sharding: By account_id if single DB becomes bottleneck.
  • Caching: Read-through cache for account metadata; never cache balance for write path.

What We Don't Change

  • Core transfer remains ACID
  • Idempotency keys required
  • Audit log immutable

Inline Check 1

What part of a payment flow should remain synchronous even at scale?

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Fintech Payment Flow – Starter →