Troubleshooting
Database connection failed: how to check the whole path
Applications often reduce a complex database failure to one generic message. Troubleshoot in layers: can the application resolve the host, reach the port, negotiate the required connection, authenticate, and access the expected database?
Confirm the destination is the database you intend to use
Check the configured hostname, port, database name, and environment. Migrations and secrets rotation can leave an application pointing at an old server even while the new database is healthy.
Test network reachability separately from credentials
If the TCP port is unreachable, changing a password will not help. Check service listening state, firewalls, security groups, bind addresses, private network routing, and DNS before authentication.
Then verify authentication and privileges
Confirm the username, password or certificate, source-host restrictions, database grants, and TLS requirements. A user can authenticate successfully but still lack permission for the schema or operation the application needs.
Check capacity when intermittent failures appear
Connection-pool exhaustion, database connection limits, CPU/memory pressure, disk issues, locks, or failovers can make some connections succeed while others fail. Correlate application and database logs with resource data.