Apple Software Engineer Interview Experience — Two Phone Screens Then a Four-Round Onsite

Phone Screen 1: Coding — Implement Hit Counter

Implement a Hit Counter that records the time of each request and can query how many hits happened in the last 5 minutes, i.e. within 300 seconds.

Main interface:

• hit(timestamp) records a request
• getHits(timestamp) returns the number of requests in the past 300 seconds

You can use a queue, or a circular buffer aggregated by second. The focus is on how to efficiently remove expired data and control the space complexity.

Phone Screen 2: System Design — Distributed Rate Limiter

Design a distributed Rate Limiter, fairly similar to the Rate Limiter problem on Hello Interview.

Mainly uses Token Bucket:

• each user or API key maps to a bucket
• the bucket has a fixed capacity
• tokens are refilled at a fixed rate

The main discussion was how to store and atomically update tokens in a distributed environment, and how to guarantee low latency and high availability.

Onsite 1: Coding Debug

A Java debugging problem. They gave me code for a KV Store scan iterator, and I needed to read through it, find the bug, and fix it.

Main things to watch for:

• the start and end range of the scan
• boundary conditions
• whether data could be missed or duplicated
• the iterator's behavior after it finishes

Onsite 2: System Design — iCloud Photo Storage

Design iCloud Photo Storage, overall similar to the S3 / Object Storage problem on Hello Interview.

Main discussion points:

• photo upload and download
• storing metadata and blob data separately
• object storage
• multi-device sync
• how hot data and cold data get loaded and stored

Onsite 3: BQ / Hiring Manager

A behavioral interview with the hiring manager, fairly standard questions — you can prep for it with Hello Interview's BQ guide.

Main topics:

• the project with the biggest impact
• an experience disagreeing with someone
• how to drive cross-team collaboration
• how to handle conflicting priorities

Onsite 4: Coding — Top K Closest Pairs

Given a sorted array: [1, 2, 4, 7, 11, 16]. The distance between two numbers is defined as: d = |a - b|. Find the Top K pairs with the smallest distance. For example, if K = 2, the result is: [(1, 2), (2, 4)], with distances 1 and 2 respectively.