Read the user@host in the error, check which mysql.user row matches, and fix wrong passwords, host patterns, anonymous users, plugins, TLS rules and locked accounts.
First-day MySQL administration. Connect safely with option files, understand user@host accounts, create application and read-only users with least privilege, use roles, and inspect sessions and basic health from the client.
Change big MySQL tables without downtime. Know which ALTERs are INSTANT, INPLACE or COPY, protect against metadata lock pile-ups, and use gh-ost or pt-online-schema-change with throttling, replica lag checks and safe cut-over.
After a failover (manual or by Orchestrator, MHA or a script), the old primary came back writable and some clients kept writing to it. Fence the old primary, measure the divergence with GTIDs, reconcile the errant transactions and rebuild it as a replica.
A schema change hangs and every query on that table queues behind it. Find the transaction holding the metadata lock with performance_schema, clear the pile-up, and run future DDL with lock timeouts, INSTANT/INPLACE or online schema change tools.
One repeatable order of checks for a slow MySQL or PostgreSQL database - host, running sessions, waits and locks, top queries, plans, engine health and connections - with the commands for both engines side by side.
Error 1213 means InnoDB found a deadlock and rolled back one transaction. Log every deadlock, read which statements and locks were involved, then fix it with consistent ordering, better indexes, shorter transactions and application retries.
Managed MySQL services differ in storage design, failover speed, replica scaling, version policy and analytics features. Check your versions, plugins and replication needs, compare services on those points within your cloud, and test failover and major upgrades before moving production.
MySQL offers several ways to survive a server failure, with different data-loss guarantees, failover speed and operational effort. Compare asynchronous and semi-synchronous replication with orchestrated failover, InnoDB Cluster/Group Replication, Galera-based clusters and managed Multi-AZ services, and decide by RPO, RTO and team skills.
The MySQL sys schema shows which indexes are never used, which duplicate others, and which statements scan full tables. Use it to drop dead weight safely with invisible indexes, add the indexes that remove full scans, and verify the result with statement digests.
Most MySQL performance comes from a well-sized buffer pool, enough redo log capacity and I/O settings that match the storage. Measure the buffer pool hit rate and working set, size redo capacity for peak write rates, set I/O capacity for SSD/cloud disks, and change settings online where MySQL allows.
The replica SQL thread stopped on a duplicate key (1062) or a missing row (1032). Find the failing transaction, decide whether skipping is safe, skip it the GTID way, check for errant transactions that will break the next failover, and verify data with checksums.
mysqld crashes during start-up with InnoDB assertion or corruption errors. Save the data directory first, read the error log, raise innodb_force_recovery one level at a time until it starts, dump the data, and rebuild a clean instance. Or restore from backup if that's faster.
Every insert and update hangs, the error log says MySQL is waiting for disk space, and the data or binlog volume is at 100%. Free space safely by purging only binary logs that all replicas and CDC tools have read, then fix retention so it doesn't happen again.
Move self-managed MySQL to Azure Database for MySQL Flexible Server. Check compatibility, create a right-sized server, do the initial load with mydumper/myloader or Azure DMS, keep it in sync with data-in replication, and cut over in minutes.
Consolidating on PostgreSQL? pgloader converts a MySQL schema and copies the data in one command. Here are the casting rules that matter, the SQL differences to fix in the application, how to validate, and how to cut over with a short freeze or CDC.
Move a large self-managed or RDS MySQL database to Aurora MySQL with minimal downtime. From RDS, use an Aurora read replica. From EC2 or on-premises, restore a Percona XtraBackup from S3 and then replicate binlogs until cut-over.
MySQL 8.0 reached end of life in April 2026, and 8.4 is the current long-term support release. Run the MySQL Shell upgrade checker, fix the changes that bite (authentication plugin defaults, removed replication syntax, changed defaults), and upgrade replicas first, then the source.
The MySQL commands and queries you use every week. Covers the mysql client and mysqladmin, server status and variables, sessions and locks, slow queries with the sys schema, InnoDB health, sizes, indexes, users, binlogs, replication with GTIDs, and backups with mysqldump, MySQL Shell and XtraBackup.
Turn on the slow query log, summarise it with mysqldumpslow or pt-query-digest, use sys schema views for live analysis, then read EXPLAIN and add the right index.
Get in when every slot is taken, see which users and hosts hold connections, kill sleepers and long queries, and right-size max_connections and pools.
Set up a MySQL replica in a DR region using GTID-based asynchronous replication. Covers seeding with the clone plugin or XtraBackup, securing the channel, monitoring lag, promoting the replica, and rebuilding replication for failback.
Build a three-node MySQL InnoDB Cluster with MySQL Shell, put MySQL Router in front of the applications, understand single-primary failover and quorum, and run status checks, switchovers and recovery.
Read SHOW REPLICA STATUS correctly, then fix the usual causes of lag, from single-threaded appliers and missing primary keys to large transactions.
Configure a single MySQL 8.4 LTS server for production. Covers the InnoDB buffer pool and redo log, durability settings, binlogs for point-in-time recovery, connection limits, slow query logging, secure users and XtraBackup.
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