What is Hash Table?
Turkish: Hash Tablosu
A hash table is a data structure that maps keys into buckets with a hash function for fast lookup, insert, and delete.
What is a Hash Table?
A hash table is a core data structure for fast access to key-value pairs. A key is passed through a hash function, and the result determines which bucket stores the value. In the average case, lookup, insert, and delete operations are close to constant time.
Many Map, Dictionary, HashMap, and object lookup implementations in programming languages are based on this idea. A common example is finding a user record quickly by user ID.
How Does It Work?
The hash function must return the same result for the same key. If two different keys land in the same bucket, a collision occurs. Collisions are handled with techniques such as chaining, open addressing, or probing.
Performance depends on hash distribution, load factor, and resizing strategy. If the function produces poor distribution and too many collisions, an operation that should be fast in theory can become slow in practice.
Business Use
Hash tables appear inside many infrastructure tasks: caching, session management, indexing, deduplication, counters, and fast configuration lookup. In an e-commerce system, finding stock information by SKU or resolving token metadata in an API gateway are typical examples.
In-memory systems such as Redis expose hash-like data structures at application level. Still, persistence, memory limits, and consistency requirements must be evaluated separately from the data structure itself.