Transactions

A transaction in Redis is a sequence of commands executed in order and atomically. The command MULTI marks the beginning of a transaction, and the command EXEC marks its end. Any commands between the MULTI and EXEC commands are serialized and executed as an atomic operation. Redis does not serve any other client in the middle of a transaction.

All commands in a transaction are queued in the client and are only sent to the server when the EXEC command is executed. It is possible to prevent a transaction from being executed by using the DISCARD command instead of EXEC. Usually, Redis clients prevent a transaction from being sent to Redis if it contains command syntax errors.

Unlike in traditional SQL databases, transactions in Redis are not rolled back if they produce failures. Redis executes the commands in order, and if any of them fail, it proceeds to the next command. Another downside of Redis transactions is that it is not possible to make any decisions inside the transaction...