EA Backend Engineer Interview: Rounds, Questions and Preparation

What the job involves

Backend engineers in global tech companies build and maintain the server-side systems that power applications, games, and services used by millions. Day to day, they write APIs, design databases, optimise performance, and ensure reliability and scalability across distributed systems. They collaborate with frontend, mobile, and data teams to deliver features end to end.

Role and Technical Knowledge

1. 1

   Explain the difference between SQL and NoSQL databases. When would you choose one over the other for a gaming backend?

   Strong answers highlight use cases: SQL for transactional integrity and complex queries, NoSQL for high-throughput, low-latency, and flexible schemas. Mention examples like player profiles (SQL) vs. real-time leaderboards (NoSQL).

2. 2

   What is a RESTful API? How does it differ from GraphQL, and which would you use for a mobile game backend?

   Cover REST principles (stateless, resource-based) and GraphQL's flexibility (single endpoint, client-specified queries). Discuss trade-offs: REST for simplicity and caching, GraphQL for reducing over-fetching in mobile apps.

3. 3

   How would you design a system to handle millions of concurrent players in an online game?

   Focus on scalability: load balancing, horizontal scaling, sharding, caching (Redis), and message queues. Mention stateless services and database replication.

4. 4

   What are the key considerations for ensuring data consistency in a distributed system?

   Discuss CAP theorem, eventual consistency, ACID vs. BASE, and techniques like two-phase commit or consensus algorithms (Raft, Paxos). Relate to game state synchronization.

Practical Scenarios

1. 5

   You notice a sudden spike in API latency during peak hours. How would you debug and resolve it?

   Outline a systematic approach: check monitoring tools (Grafana, New Relic), analyze logs, identify bottlenecks (database queries, network, CPU), and apply fixes like caching, query optimization, or scaling resources.

2. 6

   How would you handle a situation where a critical bug is found in production just before a major game launch?

   Emphasize prioritization, quick rollback if possible, hotfix deployment, and communication with stakeholders. Mention post-mortem and preventive measures.

3. 7

   Describe how you would implement rate limiting for an API to prevent abuse.

   Explain algorithms like token bucket or leaky bucket, use of Redis for distributed rate limiting, and returning 429 status codes. Discuss trade-offs between strictness and user experience.

4. 8

   You need to migrate a monolithic backend to microservices. What steps would you take?

   Cover assessment, identifying bounded contexts, incremental migration (strangler pattern), API gateways, and ensuring data consistency. Highlight testing and monitoring.

Behavioural and HR

1. 9

   Tell me about a time you worked in a team to solve a complex technical problem.

   Use STAR method: describe the situation, your role, actions taken, and results. Highlight collaboration, communication, and impact.

2. 10

   How do you handle disagreements with a teammate about the best technical approach?

   Show respect for others' opinions, data-driven decision making, and willingness to compromise. Mention seeking mentorship or prototyping to compare solutions.

3. 11

   Why do you want to work as a backend engineer in the gaming industry?

   Connect personal interest in gaming with technical challenges like scalability, real-time systems, and global impact. Show enthusiasm for the company's products.

4. 12

   Where do you see yourself in five years?

   Focus on growth: deepening technical expertise, taking on leadership, and contributing to impactful projects. Align with the company's career progression.

Problem Solving and Coding

1. 13

   Given an array of integers, find two numbers that sum to a target value. How would you optimize for time and space?

   Discuss brute force O(n^2) vs. hash map O(n) time and O(n) space. Mention edge cases like duplicates and no solution.

2. 14

   Write a function to detect a cycle in a linked list. Explain your approach.

   Cover Floyd's cycle-finding algorithm (tortoise and hare) with O(n) time and O(1) space. Discuss alternative using hash set.

3. 15

   How would you design a URL shortening service like bit.ly?

   Focus on requirements, API design, database schema, hashing (base62), and handling collisions. Mention scalability and analytics.

4. 16

   Implement a LRU cache with get and put operations in O(1) time.

   Use a combination of hash map and doubly linked list. Explain eviction policy and thread safety considerations.