Mysql Replication vs Postgresql Replication

MySQL and PostgreSQL both ship native replication, but they made opposite bets on flexibility versus correctness. Here's which one earns your trust under load.

How they actually replicate

PostgreSQL's default is physical streaming replication: the primary ships its write-ahead log (WAL) and replicas replay it block-for-block. The replica is a literal copy — same data files, same byte layout. It cannot diverge by design. MySQL replicates logically through the binary log, shipping either SQL statements or row-change events that the replica re-applies. That logical layer is genuinely powerful: cross-version replication, replicas with extra indexes, multi-source fan-in, partial replication of chosen schemas. But the replica reconstructs state rather than copying it, which is the whole reason it can drift. Postgres added logical replication (publications/subscriptions) in version 10, so it can now play MySQL's flexible game too — but its trustworthy default is still physical. The mental model: Postgres copies bytes and gives you logic as an option; MySQL copies logic and never had a physical default. That single architectural choice colors every operational decision below.

Consistency and the drift problem

This is where Postgres earns the pick. Because physical replication replays the WAL, a Postgres replica is guaranteed identical to the primary down to the page. There is no class of bug where the replica computes a different answer. MySQL's statement-based replication was a notorious source of silent divergence — non-deterministic functions, triggers, and auto-increment races meant replicas could quietly compute different values and nobody noticed until failover served wrong data. Row-based replication (now the default) fixed most of that by shipping actual row images instead of statements, and GTIDs made failover sane. So modern MySQL is far better than its reputation. But "we fixed the foot-gun" is a weaker position than "the foot-gun was never possible." Postgres never had to retrofit determinism because copying bytes is deterministic by definition. When the question is can I trust this replica, the engine that makes drift architecturally impossible wins over the one that patched it.

Failover and operations

MySQL's failover story matured hard with GTIDs and tools like Orchestrator and Group Replication — promoting a replica, re-pointing the topology, and avoiding split-brain is well-trodden, and the ecosystem of battle-scarred ops tooling is genuinely deeper. Postgres failover is more DIY: you reach for Patroni, repmgr, or a managed provider, because core Postgres gives you the primitives but not the orchestration. Replication slots prevent the primary from discarding WAL a replica still needs — great for reliability, but leave a slot orphaned and your primary's disk fills until it crashes. That's the Postgres failure mode people actually hit. MySQL's flexibility also bites: it's easier to misconfigure logical replication into a slow, lagging mess. Honest read: MySQL has the better out-of-the-box HA ecosystem, Postgres has the safer underlying guarantees. If you run managed (RDS, Cloud SQL, Aurora), both pains mostly disappear and the consistency edge dominates.

The verdict, no hedging

Pick PostgreSQL replication. Replication is insurance, and insurance you can't fully trust isn't insurance. Physical streaming gives you a replica that is provably the primary, synchronous commit gives you zero-data-loss when you ask for it, and you can still drop to logical replication when you need MySQL-style flexibility — Postgres has both modes, MySQL effectively has one. MySQL's logical model is the right tool for genuinely heterogeneous setups: multi-source fan-in, cross-version upgrades, replicas with different shapes. If that's your actual problem, run MySQL and don't apologize. But for the default case — read scaling and reliable failover — Postgres makes the worst replication bug categorically impossible, while MySQL spent a decade patching it out. "It depends" is banned here, so: unless heterogeneity is a hard requirement, replicate on Postgres and sleep better.

Quick Comparison

Factor	Mysql Replication	Postgresql Replication
Replica correctness	Logical replay; row-based fixed most drift but it was historically possible	Physical WAL replay; replica is byte-identical, drift impossible by design
Flexibility (cross-version, multi-source, partial)	Excellent — logical model bends in every direction	Physical is rigid; logical replication available but secondary
Out-of-box HA / failover ecosystem	Mature: GTIDs, Orchestrator, Group Replication	DIY: Patroni/repmgr; slots can fill the primary disk
Zero-data-loss option	Semi-sync replication, can still lose edge cases	Synchronous commit gives provable zero loss
Trust under failover	Good now, but reputation earned the hard way	Replica guaranteed equal to primary, full stop

The Verdict

Use Mysql Replication if: You need cross-version or heterogeneous replication, multi-source fan-in, or replicas that serve different schemas and indexes — MySQL's logical model bends in ways Postgres physical replication flatly refuses to.

Use Postgresql Replication if: You want a replica you can trust as an exact copy of the primary for failover and read scaling, with synchronous commit available when you need provable zero data loss.

Consider: Both are battle-tested. If your team already runs one in production, the operational muscle memory outweighs the architectural edge — don't switch engines for replication semantics alone.

The Bottom Line

Postgresql Replication wins

PostgreSQL's physical streaming replication ships byte-exact WAL, so a replica is a guaranteed bit-for-bit copy of the primary — no silent drift, no "replica says X, primary says Y" debugging sessions at 3am. MySQL's logical binlog replication is more flexible but historically tolerant of divergence, and that flexibility is exactly how production replicas quietly go wrong. For the one job replication exists to do — be correct when the primary dies — Postgres wins.

Related Comparisons