Combined RDB + AOF in Redis - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is RDB in Redis?

RDB (Redis Database) is a snapshotting method that saves the dataset to disk at specific intervals. It creates a point-in-time copy of the data.

beginner

What does AOF stand for and what is its purpose in Redis?

AOF stands for Append Only File. It logs every write operation received by the server, allowing Redis to rebuild the dataset by replaying these commands.

intermediate

Why combine RDB and AOF in Redis?

Combining RDB and AOF gives both fast recovery from snapshots (RDB) and a more complete, fine-grained log of changes (AOF), improving durability and performance.

intermediate

How does Redis use RDB and AOF together during restart?

Redis loads the RDB snapshot first for a quick dataset load, then replays the AOF log to apply any changes made after the snapshot, ensuring data is up-to-date.

advanced

What is a key advantage of using AOF with the 'every second' fsync policy?

It balances durability and performance by syncing the AOF file to disk every second, reducing data loss risk while keeping Redis fast.

What does RDB do in Redis?

A Creates snapshots of data at intervals

B Logs every write operation

C Deletes old data automatically

D Encrypts data on disk

RDB creates snapshots of the dataset at specific times to save data to disk.

What is the main benefit of AOF over RDB?

A Faster snapshot creation

B More complete data recovery by logging every write

C Uses less disk space

D Automatically compresses data

AOF logs every write operation, allowing more complete recovery than periodic snapshots.

When Redis restarts using combined RDB + AOF, what happens first?

A RDB snapshot is loaded first

B AOF log is replayed first

C Both load simultaneously

D Data is lost and rebuilt from scratch

Redis loads the RDB snapshot first for a quick start, then replays the AOF log.

Which fsync policy for AOF balances durability and performance?

A fsync always

B fsync never

C fsync every minute

D fsync every second

Fsync every second reduces data loss risk while keeping Redis fast.

Why might you use both RDB and AOF in Redis?

A To encrypt data twice

B To save disk space

C To improve data durability and recovery speed

D To avoid backups

Using both improves durability and speeds up recovery by combining snapshot and log methods.

Explain how Redis uses RDB and AOF together to ensure data durability and fast recovery.

Think about what happens during normal operation and after a restart.

Describe the advantages and disadvantages of using only RDB or only AOF for Redis persistence.

Consider data loss risk and recovery speed.