Maxmemory setting in Redis - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the maxmemory setting in Redis control?

The maxmemory setting controls the maximum amount of memory Redis can use to store data. When this limit is reached, Redis will start evicting keys based on the eviction policy.

beginner

How can you set the maxmemory limit in Redis?

You can set maxmemory in the Redis configuration file (redis.conf) using the line maxmemory <bytes>, or dynamically at runtime with the command CONFIG SET maxmemory <bytes>.

intermediate

What happens when Redis reaches the maxmemory limit?

When Redis reaches the maxmemory limit, it will evict keys according to the configured eviction policy to free up space for new data. If no eviction policy is set, Redis will return errors on writes.

intermediate

Name two common eviction policies used with Redis maxmemory setting.

Two common eviction policies are allkeys-lru (evicts least recently used keys from all keys) and volatile-lru (evicts least recently used keys only from keys with an expiration).

beginner

Why is setting maxmemory important in Redis?

Setting maxmemory helps prevent Redis from using too much system memory, which could cause the server to slow down or crash. It ensures Redis manages memory efficiently by evicting keys when needed.

What does the Redis maxmemory setting specify?

A Maximum number of keys Redis can store

B Maximum memory Redis can use

C Maximum CPU usage Redis can have

D Maximum network bandwidth Redis can use

The maxmemory setting limits the total memory Redis can use to store data.

Which command sets the maxmemory limit dynamically in Redis?

A CONFIG SET maxmemory <bytes>

B SET maxmemory <bytes>

C CONFIG GET maxmemory

D MEMORY LIMIT <bytes>

The command CONFIG SET maxmemory <bytes> sets the memory limit at runtime.

What happens if Redis reaches the maxmemory limit and no eviction policy is set?

A Redis crashes immediately

B Redis deletes all keys

C Redis automatically increases memory limit

D Redis stops accepting writes and returns errors

Without an eviction policy, Redis returns errors on write commands when memory is full.

Which eviction policy evicts the least recently used keys from all keys in Redis?

A allkeys-lru

B volatile-lru

C noeviction

D random

allkeys-lru evicts least recently used keys from all keys regardless of expiration.

Why should you configure maxmemory in Redis?

A To increase network speed

B To limit CPU usage

C To prevent Redis from using too much memory and crashing the server

D To disable key expiration

Setting maxmemory prevents Redis from using excessive memory that could harm server stability.

Explain what the Redis maxmemory setting does and why it is important.

Think about how Redis manages memory and what happens when it runs out.

Describe how Redis behaves when it reaches the maxmemory limit and how eviction policies affect this behavior.

Consider what Redis does to make space for new data when memory is full.