AOF (Append Only File) in Redis - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the AOF (Append Only File) in Redis?

AOF is used to save every write operation received by the Redis server. This helps to rebuild the database by replaying these operations after a restart, ensuring data durability.

beginner

How does Redis write data to the AOF file?

Redis appends each write command to the AOF file immediately or periodically, depending on the configured fsync policy, to keep a log of all changes.

intermediate

What are the common fsync policies for AOF in Redis?

The common fsync policies are: always (fsync after every command), everysec (fsync every second), and no (let the OS decide when to write).

intermediate

What is AOF rewriting in Redis and why is it important?

AOF rewriting creates a new, smaller AOF file by rewriting the current dataset as a minimal set of commands. This reduces file size and speeds up recovery.

intermediate

Compare AOF and RDB persistence in Redis.

AOF logs every write operation for better durability but can be slower. RDB snapshots the dataset at intervals, which is faster but risks losing recent changes.

What does AOF stand for in Redis?

A Automatic Output File

B Advanced Operation Format

C Append Only File

D Asynchronous Output Function

AOF stands for Append Only File, which logs every write operation to Redis.

Which fsync policy writes to the AOF file after every command?

A always

B every second

C no

D manual

The 'always' policy fsyncs after every command to ensure maximum durability.

What is the main benefit of AOF rewriting?

A Speeds up recovery by reducing file size

B Disables persistence

C Deletes all data

D Increases file size

AOF rewriting creates a smaller file, making recovery faster.

Which persistence method risks losing recent changes if Redis crashes?

A AOF

B RDB

C Both AOF and RDB

D None

RDB snapshots at intervals, so recent changes after the last snapshot can be lost.

How does Redis use the AOF file during restart?

A It ignores the AOF file

B It deletes the AOF file

C It converts AOF to RDB format

D It replays all commands in the AOF file to rebuild data

Redis replays the commands in the AOF file to restore the database state.

Explain how the AOF persistence works in Redis and why it is useful.

Think about how Redis saves changes to avoid data loss.

Describe the differences between AOF and RDB persistence methods in Redis.

Consider how each method saves data and the trade-offs.