Do not hold transactions across the network

Principle

Database transactions protect local consistency. Holding a transaction open while calling another service (or anything slow/unreliable) couples locks to the network and creates outages under load.

Therefore we practice

• Commit (or roll back) local work before remote I/O
• Do not call REST/RPC/gRPC inside an open DB transaction
• Do not publish to a broker inside an open transaction unless using a proven pattern (e.g. transactional outbox in the same commit)
• Keep transactions short; avoid user think-time inside a transaction
• If you need “write + notify,” use outbox/CDC or a workflow — not BEGIN → HTTP → COMMIT

Smells

• Connection pool exhaustion when a dependency slows down
• Timeouts cascading while rows stay locked
• “It works in staging” with low concurrency and fails on Black Friday
• Compensating for distributed locks that only exist because the transaction was too wide