What is memoization and when would you use it in front-end or back-end code?

What is memoization and when would you use it in front-end or back-end code?

• A. Memoization stores results in a database for long-term persistence.
• B. Memoization duplicates memory to speed up I/O operations.
• C. Memoization computes all possible inputs in advance and stores them in cache.
• D. Memoization caches results of expensive function calls for given inputs to avoid recomputation; used in performance-critical code paths.

Answer: (D)

Memoization is a caching technique that stores the results of expensive function calls in memory the first time they run, keyed by their inputs. When the same inputs appear again, the cached result is returned instead of redoing the calculation. This speeds up performance in paths where a function is called repeatedly with the same arguments, which can occur on both front-end and back-end.

It's typically in-process and lazy: you don’t precompute everything or persist data to disk; you compute on demand and keep the result for future reuse. Use memoization for costly computations or data transformations that recur with the same inputs, while being mindful of memory usage and cache invalidation—if inputs can change or freshness matters, you’ll need a strategy to clear or update the cache. For example, a heavy calculation in a UI render or a server-side function that processes the same payload multiple times can benefit from memoization.