In-memory caching patterns in Node.js - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is in-memory caching in Node.js?

In-memory caching stores data temporarily inside the server's memory to quickly reuse it without fetching or computing again. It helps speed up apps by avoiding slow operations.

beginner

Name a common data structure used for in-memory caching in Node.js.

A JavaScript object or Map is often used to hold cached data as key-value pairs for fast lookup.

intermediate

What is the purpose of a cache expiration or TTL (time-to-live)?

TTL sets how long cached data stays valid. After that, the cache removes or refreshes the data to keep it fresh and avoid stale info.

intermediate

Explain the 'lazy loading' caching pattern.

Lazy loading means the cache only loads data when first requested. If data is missing, the app fetches it, stores it in cache, then returns it.

advanced

What is the difference between write-through and write-back caching?

Write-through updates cache and main storage at the same time, ensuring consistency. Write-back updates cache first and writes to storage later, improving speed but risking data loss.

Which data structure is best for fast key-value caching in Node.js?

A Map

B Array

C Set

D String

Map provides fast key-value access and better performance than arrays for caching.

What does TTL stand for in caching?

A Time To Live

B Total Time Limit

C Time To Load

D Temporary Transfer Limit

TTL means Time To Live, the duration cached data remains valid.

In lazy loading caching, when is data loaded into the cache?

A At server startup

B Never loaded

C Every minute automatically

D Only when requested

Lazy loading caches data only when it is first requested.

Which caching pattern updates the main storage immediately when cache changes?

A Write-back

B Write-through

C Lazy loading

D Cache-aside

Write-through caching updates both cache and storage at the same time.

What is a risk of using write-back caching?

A Slower writes

B Cache is always stale

C Data loss if server crashes before storage update

D Cache never updates

Write-back caching risks data loss if the server crashes before writing to storage.

Describe how you would implement a simple in-memory cache in Node.js with expiration.

Think about storing data with time info and checking it on each request.

Explain the differences and use cases for write-through and write-back caching patterns.

Consider speed versus data safety trade-offs.