Sync vs async

Learn synchronous and asynchronous replication.

Sync and async

Synchronous replication does not finish a write until the slave acknowledges; consistent but slower. Asynchronous skips the wait; faster but with a brief lag.

ALTER SUBSCRIPTION sub_orders
SET (synchronous_commit = on);

Sync is consistent, async is fast.

Sync and async — details

Financial systems prefer synchronous: lost data is unacceptable. Analytical systems accept asynchronous; a brief lag is fine and performance matters more.

Exercise Sync and async

Make the sub_orders subscription synchronous: SET (synchronous_commit = on).

Show example solution

ALTER SUBSCRIPTION sub_orders SET (synchronous_commit = on);

Test yourself

Sync vs async: match the terms

sync

sync
async

async
acknowledge

ack
lag

lag

Sync setting

ALTER SUBSCRIPTION sub_orders SET (synchronous_commit = ____)

Show answer

ALTER SUBSCRIPTION sub_orders SET (synchronous_commit = on)

What does synchronous replication wait for?
- The backup to finish
- User input
- The disk to fill up
- Confirmation from the replica
Show answer

Confirmation from the replica — Synchronous replication waits for slave acknowledgement.

Next lesson: What is sharding?

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