A database failover can preserve uptime and break the answer

A PostgreSQL MCP server can remain available during failover and still return the wrong answer, as connection retries against a replica that is behind can combine pre- and post-failover results. The developer recommends giving each workflow a consistency contract and testing failover consistency, not only availability.

A PostgreSQL MCP server can remain available during failover and still return the wrong answer. The connection retries against a replica. The replica is behind. A conversation combines a pre-failover result with a post-failover follow-up. Every query succeeds, so the final answer looks complete. Before production, give each workflow a consistency contract: Then make source identity, schema version, snapshot marker, observed time, and freshness part of material results. Test more than promotion: Never concatenate partial rows from the old primary with rows from the new one. If the answer cannot prove one consistency boundary, discard the partial result and return a structured retryable failure. Availability is a transport property. Trustworthy answers need a data contract. Full test guide: MCP server for Postgres: test failover consistency, not only availability https://conexor.io/blog/mcp-server-postgres-failover-consistency-test?utm source=devto&utm medium=article&utm campaign=content