PostgreSQL failover can keep servers online while silently corrupting query answers

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A PostgreSQL MCP server can stay available during a database failover yet return incorrect results by retrying connections against a lagging replica. This means individual queries succeed without errors, but responses may mix pre- and post-failover data, making flawed answers appear complete and trustworthy. Experts warn that availability is a transport-layer property and does not guarantee data correctness or consistency. To address this, each workflow should be assigned a consistency contract — such as monotonic reads or read-your-writes — before going into production. Partial results that cannot be tied to a single consistency boundary should be discarded and returned as structured, retryable failures rather than silently served to users.

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ProgrammingDEV Community ·

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