title: Hazelcast: What would be the implications of adding indexes to huge existing IMaps?
body: <p>Given 4-5 nodes having many IMaps with lots of data in it, some of the predicate queries started to become significantly slow. One of the solutions for solving this performance issue (as I think) could be adding indexes. However, this data is part of a sensible system which is currently being used in production.</p>
  
  <p>Before adding indexes, I was wondering what would be the consequences of doing it on huge IMaps? (would it lock the entire map ?; would it bring down the entire system?; etc.) Hazelcast documentation includes information about how to do it, but doesn't give any other explanation.</p>