Database timeout

Updated 11 October 2026

Short answer

A database timeout means something waited longer than its limit: either a query took too long to run, or the app couldn't get a connection in time. The usual cause is one slow query, often on a table that has grown, or one missing an index, or rows locked by another long operation. Turn on slow-query logging to find it, then fix the query or add the index.

What's the problem

Pages are slow and then fail with "query timeout", "statement timeout", "Lock wait timeout exceeded", "MySQL server has gone away" or a 504. Often only some pages, or only at busy times.

Why it happens

  • A slow query: scanning a whole large table because there's no index for it.
  • Lock waits: one long operation (an import, a report, a migration) holds locks other queries need.
  • An overloaded database: CPU or disk at its limit.
  • Idle connections closed by the server, then reused by the app ("gone away").
  • Network problems between app and database.

How to fix it

  1. Turn on slow-query logging. PostgreSQL: log_min_duration_statement. MySQL: the slow query log.
  2. Find the slowest and most frequent queries, and run them with EXPLAIN to see whether they use an index.
  3. Add the missing index, or rewrite the query to fetch less.
  4. Move long jobs off busy times or into background workers.
  5. Check database CPU, memory and disk in your provider's dashboard.
  6. Configure your app's pool to check connections before reusing them.

What Preventionlabs checks

One click runs the full report on your domain. For this problem it shows whether your site loads, how fast, and where its redirects go; uptime checked every 5 minutes, with an email when the site goes down and when it is back. With Cloudflare connected, it also shows which pages returned server errors (5xx) to visitors, and when; recent deploys and account changes, with their times. It can't connect to your database, so the database error itself is in your host's or database provider's logs.

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Sources

  1. PostgreSQL: Client Connection Defaultsofficial docsAbort any statement that takes more than the specified amount of time.
  2. PostgreSQL: Error Reporting and Loggingofficial docsCauses the duration of each completed statement to be logged if the statement ran for at least the specified amount of time.
  3. MySQL: MySQL server has gone awayofficial docsThe most common reason for the MySQL server has gone away error is that the server timed out and closed the connection.

Related

504 Gateway Timeout Your app took too long to answer and the server in front of it gave up. Usually a slow database query, a slow outside API, or an overloaded server. "Too many connections" database error Every database connection is in use. Usually your app opens connections and doesn't close them, or traffic outgrew the limit. Fix leaks first. Why is my website slow? Find out which part is slow: the server producing the page, or the browser loading heavy files. Measure first, then fix the slowest part. Cloudflare error 524: a timeout occurred Error 524: your server accepted the request but took longer than Cloudflare's 125-second limit to answer. Find the slow page and the slow step in it.
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