16 lines
692 B
Markdown
16 lines
692 B
Markdown
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# ADR-0004: Postgres transactional outbox first, Kafka later
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**Status**: accepted · 2026-09
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**Context**: Event bus carries business objects (P4) and is the audit backbone
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(P5). Phase-1 volume is bid-frequency, not telemetry-frequency.
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**Decision**: Phase 1 uses a Postgres transactional outbox (business write +
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event in one transaction) with polling/LISTEN consumers, behind a thin bus
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interface. Phase 2 relays the outbox into Kafka when telemetry-scale events
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arrive; consumer interface unchanged.
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**Consequences**: Exactly-once-ish semantics via same-DB transactionality in
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phase 1; events reconcile trivially against business data. Bus abstraction must
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not leak Postgres specifics.
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