Without pool_pre_ping, stale pooled connections (left over after a Postgres
restart or network blip) cause immediate query failures. SQLAlchemy then
propagates the error rather than transparently reconnecting, which crashes
the Quart request handler and triggers a Swarm restart loop.
- pool_pre_ping=True: issues a lightweight SELECT 1 before each checkout;
discards and replaces stale connections silently
- pool_recycle=1800: recycles connections every 30 minutes to prevent
long-idle connections from going stale at the TCP/firewall level
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
bvandeusen
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