Instacart Senior Software Engineer Core Experience interview questions

The coding interview was conducted on HackerRank and lasted 90 minutes. It focused on building a simplified banking system through one base problem with four follow-up extensions that increased in complexity. The questions involved implementing account creation, deposits, and transfers, followed by ranking logic based on transactions, time-delayed cashback payments, and maintaining accurate transaction history. The problems emphasized clean state management, correctness across time-based operations, and designing extensible logic under pressure. No system design or behavioral questions were asked—this was a purely implementation-focused interview.