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Grokking Node.js Design Patterns for Interviews

Problem: Unify Cache Clients

Medium
30 min
Wrap multiple cache backends (in-memory and Redis-like) under a single unified API.

Problem statement

Your application uses two cache systems depending on the environment:

  • In-memory cache in development, for simplicity.

  • Redis-like cache in production, which stores data asynchronously.

The problem is that both systems expose different method names and behaviors.

  • The in-memory cache uses synchronous methods:

setItem(key, value)
getItem(key)

  • The Redis-like client uses async methods:

async set(key, value)
async get(key)

You need a way for the rest of your app to talk to any cache with a single, consistent interface, without conditionals spread across the codebase.

Goal

Implement a CacheAdapter class that exposes two methods:

  • async set(key, value)

  • async get(key)

The adapter should:

  • Wrap either the in-memory or Redis-like client.

  • Normalize sync vs. async behavior so both can be awaited.

  • Return the same kind of results regardless of the underlying cache.

Constraints

  • You cannot modify the original cache clients.

  • The adapter must detect which methods are available.

  • All cache operations should work with await syntax.

  • The adapter must detect which methods are available.

Sample output

The examples below illustrate what the output should look like:

(async () => {
  const memory = new CacheAdapter(memoryCache);
  const redis = new CacheAdapter(redisCache);
  await memory.set('user', 'Alice');
  await redis.set('user', 'Bob');
  console.log(await memory.get('user'));
  console.log(await redis.get('user'));
})();
/* Expected output:
Alice
Bob
*/

Good luck trying the problem! If you’re unsure how to proceed, check the “Solution” tab above.

Similar Problems
Unify HTTP Client Responses
Normalize Logger Interfaces
Standardize File Storage Clients
Bridge Callback and Promise APIs
Adapt Configuration Sources
Compose Nested Adapters
Hybrid Service Adapter for Fallback APIs
Asynchronous Streaming Adapter
Home
Courses
Grokking Node.js Design Patterns for Interviews

Problem: Unify Cache Clients

Medium
30 min
Wrap multiple cache backends (in-memory and Redis-like) under a single unified API.

Problem statement

Your application uses two cache systems depending on the environment:

  • In-memory cache in development, for simplicity.

  • Redis-like cache in production, which stores data asynchronously.

The problem is that both systems expose different method names and behaviors.

  • The in-memory cache uses synchronous methods:

setItem(key, value)
getItem(key)

  • The Redis-like client uses async methods:

async set(key, value)
async get(key)

You need a way for the rest of your app to talk to any cache with a single, consistent interface, without conditionals spread across the codebase.

Goal

Implement a CacheAdapter class that exposes two methods:

  • async set(key, value)

  • async get(key)

The adapter should:

  • Wrap either the in-memory or Redis-like client.

  • Normalize sync vs. async behavior so both can be awaited.

  • Return the same kind of results regardless of the underlying cache.

Constraints

  • You cannot modify the original cache clients.

  • The adapter must detect which methods are available.

  • All cache operations should work with await syntax.

  • The adapter must detect which methods are available.

Sample output

The examples below illustrate what the output should look like:

(async () => {
  const memory = new CacheAdapter(memoryCache);
  const redis = new CacheAdapter(redisCache);
  await memory.set('user', 'Alice');
  await redis.set('user', 'Bob');
  console.log(await memory.get('user'));
  console.log(await redis.get('user'));
})();
/* Expected output:
Alice
Bob
*/

Good luck trying the problem! If you’re unsure how to proceed, check the “Solution” tab above.

Similar Problems
Unify HTTP Client Responses
Normalize Logger Interfaces
Standardize File Storage Clients
Bridge Callback and Promise APIs
Adapt Configuration Sources
Compose Nested Adapters
Hybrid Service Adapter for Fallback APIs
Asynchronous Streaming Adapter
Node.js
// Simulated in-memory cache
const memoryCache = {
  store: {},
  setItem(key, value) {
    this.store[key] = value;
    return true;
  },
  getItem(key) {
    return this.store[key] ?? null;
  }
};
// Simulated async Redis-like cache
const redisCache = {
  store: {},
  async set(key, value) {
    return new Promise(resolve => {
      setTimeout(() => {
        this.store[key] = value;
        resolve('OK');
      }, 100);
    });
  },
  async get(key) {
    return new Promise(resolve => {
      setTimeout(() => {
        resolve(this.store[key] ?? null);
      }, 100);
    });
  }
};
// Your code here
// Example usage
(async () => {
  const memory = new CacheAdapter(memoryCache);
  const redis = new CacheAdapter(redisCache);
  await memory.set('user', 'Alice');
  await redis.set('user', 'Bob');
  console.log(await memory.get('user'));
  console.log(await redis.get('user'));
})();
/* Expected output:
Alice
Bob
*/