All 15 Caching questions
More in Caching
What is the difference between res.set('Cache-Control', 'no-cache') and 'no-store' in an Express response? What is the difference between in-memory caching (like a Map or node-cache) and a distributed cache (like Redis)? What HTTP caching headers (Cache-Control, ETag) can a Node.js/Express API use to let clients and CDNs cache responses? How would you implement a Least Recently Used (LRU) cache in Node.js, and why is eviction necessary for an in-memory cache? How would you cache the result of a database query in Node.js while ensuring the cache is properly invalidated when the underlying data changes? What is the risk of caching sensitive or user-specific data with a shared cache key, and how do you avoid it? What is negative caching, and why might you deliberately cache the fact that a lookup returned 'not found'? What are the main cache invalidation strategies (TTL, write-through, cache-aside), and when is each appropriate? What is cache stampede (thundering herd), and how do you prevent it in a high-traffic Node.js service? What is Redis's EXPIRE and how do TTL-based keys interact with Redis's own memory eviction policies under memory pressure?
Advertisement
Back to results for “Functional Programming”
Node.js › Caching

What is memoization, and how does it differ from a general-purpose external cache like Redis?

Intermediate

Answer

Memoization caches the return value of a specific pure function based on its input arguments, entirely within the process's memory and scoped to that function -- a code-level optimization for avoiding redundant computation, whereas an external cache like Redis is a general-purpose, application-wide (and often multi-process) data store used for a much broader range of caching needs beyond a single function call.
function memoize(fn) {
  const cache = new Map();
  return (...args) => {
    const key = JSON.stringify(args);
    if (cache.has(key)) return cache.get(key);
    const result = fn(...args);
    cache.set(key, result);
    return result;
  };
}
Real-world example A pricing-calculation function performing an expensive deterministic computation based on a product's attributes is wrapped in a memoization helper, speeding up repeated calls for the same product configuration within a single process.

Common follow-ups: Why is memoization only safe for pure, deterministic functions with no side effects?;What's the risk of memoizing a function whose input arguments are complex objects, given JSON.stringify-based key generation?

Performance Optimization & Profiling;Functional Programming
All 15 Caching questions