In-memory caching with node-cache in Express - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is in-memory caching in the context of a Node.js server?

In-memory caching stores data temporarily inside the server's memory (RAM) to quickly serve repeated requests without recalculating or fetching from a database.

beginner

What is the main purpose of the node-cache library?

node-cache provides a simple way to store and retrieve data in memory with expiration times, helping improve app speed by avoiding repeated heavy operations.

intermediate

How do you set a value in node-cache with a time-to-live (TTL)?

Use cache.set(key, value, ttlInSeconds). The TTL defines how long the data stays in cache before it expires.

intermediate

What happens when you try to get a key from node-cache that has expired or does not exist?

The get method returns undefined, indicating the data is not available in cache and may need to be fetched or recalculated.

beginner

Why is in-memory caching not suitable for storing very large data or permanent storage?

Because memory is limited and data is lost when the server restarts, in-memory caching is best for small, temporary data to speed up responses.

Which of the following best describes node-cache?

A A library to store data temporarily in server memory with expiration.

B A database for permanent data storage.

C A tool to compress files on the server.

D A frontend UI framework.

node-cache is used for temporary in-memory data storage with TTL, not permanent storage or UI.

How do you retrieve a cached value using node-cache?

A cache.set(key)

B cache.get(key)

C cache.delete(key)

D cache.fetch(key)

The get method retrieves the value stored under the given key.

What does TTL stand for in caching?

A Time To Live

B Total Time Limit

C Temporary Transfer Link

D Timed Token Lock

TTL means Time To Live, the duration data stays valid in cache.

If a cached item expires, what will cache.get(key) return?

A null

B empty string

C false

D undefined

Expired or missing keys return undefined in node-cache.

Which scenario is best suited for using node-cache?

A Saving large video files.

B Storing user passwords permanently.

C Caching API responses to reduce database calls.

D Hosting a website's static files.

Caching API responses temporarily speeds up repeated requests without permanent storage.

Explain how you would use node-cache to improve performance in an Express app.

Think about saving repeated data to avoid slow operations.

What are the limitations of using in-memory caching with node-cache?

Consider what happens when the server stops or restarts.