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Distributed Systems Interview Questions — What Senior Engineers Need to Know

Distributed systems questions are where senior interviews get serious. Interviewers want to see that you understand the fundamental impossibility results, the real-world trade-offs between consistency and availability, and how production systems actually handle failures like network partitions and node crashes.

These 14 questions cover the distributed systems concepts that come up repeatedly in senior-level interviews: consensus protocols, leader election, vector clocks, eventual consistency, and the practical differences between CP and AP system designs. Each question rewards depth over breadth.

All 14 Questions

Consistent HashingWhat is consistent hashing and why is it used?Rate LimitingHow do you implement rate limiting and what algorithms exist?CDNWhat is a CDN and how does it work?Load Balancer — L4 vs L7What is the difference between L4 and L7 load balancers?Distributed Transactions — 2PC, SagaWhat are 2PC and Saga patterns for distributed transactions?Exactly-once DeliveryIs exactly-once delivery possible and how do you achieve it?Leader ElectionHow does leader election work in distributed systems?Feed FanoutWhat is feed fanout and what are the push vs pull approaches?RPO / RTOWhat are RPO and RTO and why do they matter?Circuit Breaker — 3 StatesWhat is the circuit breaker pattern and what are its three states?Load Balancing AlgorithmsWhat are the common load balancing algorithms?Push CDN vs Pull CDNWhat is the difference between a push CDN and a pull CDN?CDN InvalidationHow does CDN cache invalidation work?Load Balancer FailoverHow does load balancer failover work?

How to Prepare

Focus on understanding concepts deeply enough to explain them in your own words. For each topic, practice articulating the trade-offs and real-world applications — interviewers care about practical judgment, not textbook definitions.

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