Transactions, Scripting, and PipelinesLesson 5.1

Redis transactions with MULTI and EXEC: atomic command batches

MULTI, EXEC, DISCARD, command queuing, all-or-nothing execution, error handling in transactions, no rollback on runtime errors

Transactions in Redis

Redis transactions group commands into a block. Commands between MULTI and EXEC are queued and executed atomically - no other client can interleave commands during execution.

Basic transaction

MULTI
INCR balance:alice
DECR balance:bob
EXEC
# → [1, -1] (array of results in order)

Discarding a transaction

MULTI
INCR balance:alice
DISCARD   # clears the queue, rolls back nothing (nothing was written)

Important limitation: no rollback

Redis transactions do NOT roll back on runtime errors. If one command fails mid-EXEC (e.g., calling INCR on a non-integer), Redis continues executing the remaining commands. Only syntax errors during queuing abort the entire transaction.

MULTI
SET x 10
INCR not_a_number_key   # will fail at runtime
SET y 20
EXEC
# SET x → OK  (executed)
# INCR → error  (failed)
# SET y → OK  (still executed)

This differs from SQL transactions. Redis sacrifices ACID rollback for simplicity and speed. Use WATCH (next lesson) when you need conditional atomicity.