Cache stampede prevention in Redis - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a cache stampede?

A cache stampede happens when many requests try to get the same data from the cache at the same time, but the data is missing or expired, causing all requests to hit the database simultaneously.

beginner

How does using a lock help prevent cache stampede?

A lock allows only one request to fetch and update the cache while others wait, preventing many requests from hitting the database at once.

intermediate

What is the 'early recomputation' strategy in cache stampede prevention?

Early recomputation means refreshing the cache before it expires, so requests always get fresh data and avoid many cache misses at once.

intermediate

Explain the 'request coalescing' technique.

Request coalescing groups multiple requests for the same missing cache data so only one fetches from the database, and others wait for the result.

intermediate

What Redis feature can be used to implement locking for cache stampede prevention?

Redis supports commands like SET with NX and EX options to create locks that expire automatically, helping to implement distributed locks.

What causes a cache stampede?

A Only one request accesses the cache

B Cache data is too large

C Cache is never updated

D Many requests miss the cache and hit the database simultaneously

A cache stampede happens when many requests miss the cache at the same time and all query the database.

Which Redis command option helps create a lock that only sets if the key does not exist?

A EXPIRE NX

B GET EX

C SET NX

D DEL NX

SET NX sets the key only if it does not exist, useful for locking.

What is the main benefit of early recomputation in cache management?

A Deletes cache faster

B Avoids many cache misses at once

C Increases database load

D Prevents cache from storing data

Early recomputation refreshes cache before expiry to avoid many misses simultaneously.

Request coalescing means:

A Combining multiple requests to fetch data once

B Deleting cache entries quickly

C Ignoring cache misses

D Storing duplicate cache data

Request coalescing groups requests so only one fetches data, reducing load.

Why use locks in cache stampede prevention?

A To allow only one request to update cache at a time

B To block all requests permanently

C To delete cache data randomly

D To increase cache size

Locks ensure only one request updates cache, preventing many database hits.

Describe what a cache stampede is and why it is a problem.

Think about what happens when many users ask for the same data but the cache is empty.

Explain two methods to prevent cache stampede using Redis.

Consider how Redis commands can help control access and timing of cache updates.