Cache invalidation strategies in Express - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is cache invalidation in the context of Express applications?

Cache invalidation is the process of removing or updating stored data in the cache when the original data changes, ensuring users get fresh and accurate information.

beginner

Name three common cache invalidation strategies used in Express apps.

1. Time-based expiration (TTL)<br>2. Manual invalidation (on data change)<br>3. Event-driven invalidation (triggered by events or hooks)

beginner

How does time-based expiration (TTL) work for cache invalidation?

It sets a time limit for cached data. After this time (TTL - Time To Live) expires, the cache is automatically cleared or refreshed.

intermediate

What is manual cache invalidation and when would you use it?

Manual invalidation means explicitly clearing or updating the cache when data changes, such as after a database update. Use it when data changes are known and you want precise control.

intermediate

Explain event-driven cache invalidation in Express.

Event-driven invalidation uses events or hooks in your app to clear or update cache automatically when certain actions happen, like saving new data or deleting records.

Which cache invalidation strategy automatically clears cache after a set time?

A Lazy loading

B Manual invalidation

C Event-driven invalidation

D Time-based expiration (TTL)

Time-based expiration uses a set time limit to clear cached data automatically.

When should manual cache invalidation be used in Express?

A When you want precise control after data updates

B When data changes are unpredictable

C When you want automatic cache clearing

D When cache never expires

Manual invalidation is best when you want to clear cache exactly after data changes.

What triggers event-driven cache invalidation?

A Specific app events or hooks

B A fixed timer

C User requests

D Random intervals

Event-driven invalidation happens when specific events or hooks in the app occur.

Which strategy might cause stale data if not carefully managed?

A Manual invalidation

B Time-based expiration with long TTL

C Event-driven invalidation

D No caching

Long TTL can keep stale data in cache longer before refreshing.

In Express, what is a common tool to implement caching and invalidation?

A Node.js File System

B MongoDB

C Redis

D Express Router

Redis is often used as a fast cache store with support for expiration and invalidation.

Describe the main cache invalidation strategies you can use in an Express app and when to use each.

Think about automatic vs manual ways to clear cache.

Explain why cache invalidation is important and what could happen if it is not done properly in a web app.

Consider user experience and data accuracy.