Notes for the problems that show up after launch: bad plans, awkward migrations, index debt, vacuum pressure, replica lag, and the small decisions that make PostgreSQL easier to operate.
The backups had been succeeding for eight months; the restores had never been tried. FULL/DIFF/LOG chain design as an RPO/RTO contract, what silently breaks the log chain, and why only a restore drill proves anything.
An eighteen-second JSON_EXTRACT scan dropped to single-digit milliseconds with one generated column and one index. VIRTUAL vs PERSISTENT, the real indexing rules, and the replica determinism caveats nobody mentions.
MySQL partitioning works until it collides with foreign keys; PostgreSQL's declarative partitioning composes with the rest of the schema. A practitioner's comparison of pruning, partition-wise operations, and maintenance.
Purge lag is usually a pinned read view, not weak purge threads. Here is how to tell the two failures apart, what innodb_purge_threads actually buys, and the alerts that matter.
A deploy 'removed' three hundred analysts' access without revoking anything — the role was granted but never active at login. MariaDB roles done right: SET DEFAULT ROLE, PUBLIC in 10.11, and auditing effective privileges.
Two API requests forty milliseconds apart booked the same room: both ran the availability SELECT, both saw zero conflicts, both inserted. EXCLUDE USING gist deleted that race window entirely.
MySQL 5.7 has been end-of-life since October 2023, and plenty of production fleets still run it. Field notes on the upgrade checker, the removals that actually break apps, and a rollback plan that is honest about being a restore plan.
A Galera node rejoin either streams a small delta (IST) or copies the entire dataset (SST), and whether any donor's gcache still holds the joiner's missing writesets decides which. Here is how the decision is made, how to size for it, and how to watch it happen.
Most MySQL-vs-PostgreSQL benchmarks are decided before the first query runs, by defaults, durability settings, and tool choice. Here is how to run a comparison that actually predicts your production behavior.
You partitioned the table by month and the queries got no faster, because EXPLAIN still lists all 48 partitions in the plan. Here is why pruning fails and the rewrites that bring it back.
We replaced a 40 GB B-tree on created_at with a 40 MB BRIN and the time-range queries got faster, not slower. Here is how to pick between B-tree, BRIN, GIN, GiST, and hash by query shape.
Most MySQL SQL runs on PostgreSQL unchanged. This post catalogs the part that does not: quoting, upserts, LIMIT, GROUP BY strictness, string functions, and the silent integer division trap.