Ever wondered what your IDE is doing when it says „Indexing” and eats up all your CPU? I’ll explain the role and implementation of the ENSIME binary indexer, and introduce you to the Graphpocalypse – our 2016 Google Summer of Code project. Although Scala IDE and Intellij use a different indexing implementation (tied into their framework), many of the principles are the same. This talk will give you an appreciation of the work your IDE is doing to enable various features that you may take for granted.