Custom cache keys in NestJS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a custom cache key in NestJS caching?

A custom cache key is a user-defined string or value used to uniquely identify cached data instead of the default key. It helps control how data is stored and retrieved from the cache.

beginner

Why would you use a custom cache key in NestJS?

You use a custom cache key to avoid collisions, organize cached data better, or include dynamic parts like user IDs or query parameters to cache different results separately.

intermediate

How do you define a custom cache key in a NestJS @Cacheable decorator?

You provide a function to the 'key' property in the @Cacheable decorator options. This function returns a string that will be used as the cache key based on method arguments or other logic.

intermediate

Example: What does this custom cache key function do? key: (args) => `user_${args[0]}_data`

It creates a cache key by taking the first argument (usually a user ID) and making a string like 'user_123_data'. This caches data specific to each user separately.

beginner

What happens if you don't use a custom cache key in NestJS caching?

NestJS uses a default key based on the method name and arguments. This can cause cache collisions or less control over cache entries, especially when arguments are complex or dynamic.

What is the main purpose of a custom cache key in NestJS?

A To disable caching

B To uniquely identify cached data

C To increase server memory

D To log cache hits

Custom cache keys uniquely identify cached data to avoid collisions and organize cache entries.

How do you specify a custom cache key in NestJS caching decorators?

A By renaming the cache folder

B By setting a global environment variable

C By passing a function to the 'key' option

D By using a special cache service method

You specify a custom cache key by providing a function to the 'key' option in the caching decorator.

Which of these is a good example of a custom cache key for user data?

A profile_cache

B cache_default

C data123

D user_${userId}_profile

A key like `user_${userId}_profile` uniquely identifies cache entries per user.

What could happen if you don't use custom cache keys when caching dynamic data?

A Cache collisions and incorrect data retrieval

B Faster cache performance

C Automatic cache clearing

D No caching at all

Without custom keys, different data might overwrite each other causing wrong data to be served.

In NestJS, the custom cache key function receives what as input?

A The method arguments

B The server configuration

C The cache store instance

D The HTTP request headers

The custom cache key function receives the method arguments to build a unique key.

Explain how to create and use a custom cache key in NestJS caching.

Think about how to make cache keys unique per input.

Why is it important to use custom cache keys when caching data that depends on user input?

Consider what happens if all users share the same cache key.