distributed systems
9 minIdempotency and the Transactional Outbox: Making Retries Safe
Learn why network retries create duplicate effects and how idempotency keys and an outbox close common reliability gaps.
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Q&A
Q&AHow does a transactional outbox make event publishing reliable?
Persist the business change and an event record together, then publish the event asynchronously.
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A database transaction writes both the business state and an outbox row. A separate publisher retries delivery from that durable row. This avoids the gap where a database commit succeeds but broker publication fails. Delivery can still be repeated, so consumers should deduplicate by a stable event ID.
Q&A
Q&AWhat does a large TCP TIME_WAIT count mean?
TIME_WAIT is part of safe TCP teardown; verify actual ephemeral-port pressure before tuning sysctls.
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TIME_WAIT helps prevent delayed packets from an old connection from contaminating a new one. A high count can be normal. Diagnose port exhaustion by checking outbound tuple reuse, NAT limits, ephemeral port range, and connection pooling. tcp_tw_reuse semantics vary by kernel and are not a universal first fix.