Upgrading to MySQL 8.4 LTS: What You Need to Know

MySQL 8.0 reached end of life in April 2026, so it no longer receives security fixes. The current long-term support line is MySQL 8.4 LTS.

The new release model

• LTS releases (8.4) - long support with bug and security fixes only. The right choice for production.
• Innovation releases (9.x) - new features every few months, short support. For trying features early.

Authentication changes

The old mysql_native_password plugin is disabled by default in 8.4 (and removed in 9.x). Accounts should use caching_sha2_password, the default since 8.0.

-- Find accounts still using the old plugin
SELECT user, host, plugin FROM mysql.user WHERE plugin = 'mysql_native_password';

-- Switch an account
ALTER USER 'app'@'%' IDENTIFIED WITH caching_sha2_password BY 'new-strong-password';

Make sure your client libraries support caching_sha2_password; current versions of mysql2 (Node.js), PyMySQL, the official connectors and PHP's mysqlnd do. Connections need TLS, or RSA key exchange, for the first authentication.

Other things to check

• Removed and deprecated system variables and options in your my.cnf; the server won't start with unknown options.
• Changed defaults (for example some InnoDB settings) that may affect performance; compare with your tuned values.
• Replication terminology: SOURCE/REPLICA commands replace the old MASTER/SLAVE forms.

A safe upgrade plan

1. Run the MySQL Shell upgrade checker: util.checkForServerUpgrade().
2. Restore a recent backup into an 8.4 staging server and run your test suite and real traffic replays.
3. Upgrade replicas first, verify, then fail over to an upgraded replica.
4. Keep the old primary around until you're confident, as a fallback.

On managed services (RDS, Cloud SQL, Azure), use the provider's major-version upgrade feature, which often supports blue/green deployments to make switching back easy.