JetBrains

2 design problems known to be asked at JetBrains.

Medium1

Mediumlow level design design patterns oop

Memento Pattern: Undo Without Cracking the Object Open

Every undo, savepoint, and game save has the same problem — capture an object's private state so you can restore it later, without letting the thing holding the snapshot read or corrupt what's inside.

Asked at Microsoft, Google, JetBrains +3

Aug 8, 2026·14 min read

Hard1

Hardlow level design design patterns oop

Visitor Pattern: Add Operations Without Editing the Classes

When your class hierarchy is stable but you keep bolting new operations onto every node — typecheck, pretty-print, evaluate, export — the Visitor pattern moves each operation into its own class so the nodes never change again.

Asked at Google, Microsoft, Amazon +3

Aug 8, 2026·15 min read