One of the most used data structures across programming languages is the hash table. In Java, the HashMap class is a hash table implementation that provides a powerful means to store and retrieve…

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The post discusses a case study from Aladdin Wealth Tech, detailing how they identified and fixed a performance issue with a Java hash table handling very large portfolios in an Apache Spark job. It was discovered that hash collisions in the Apache Commons Lang3 Pair class were causing quadratic time complexity (O(N2)). By restructuring their map keys and avoiding the use of problematic hash functions, they restored the expected performance. This experience underscores the importance of understanding data structures and their underlying mechanics to prevent such issues.

Solving the Mystery of the Slow Hash Table