System Design: Interview Prep Guide

Key system design building blocks — explained the way interviewers expect you to defend them.

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What's Covered

Topic	Key Concepts
Message Queues	Producers, Consumers, ACKs, Delivery Guarantees, Partitioning, Backpressure, DLQ, Kafka, SQS, RabbitMQ

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The System Design Interview Mindset

Interviewers aren't just checking if you know the technology.
They want to see:

  1. You can identify WHY a component is needed (motivating problem)
  2. You know HOW it works under the hood (not just "use Kafka")
  3. You can reason about trade-offs (ordering vs throughput)
  4. You've thought about failure modes (what happens when X breaks?)
  5. You know when NOT to use something

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Common System Design Components (Mindmap)

mindmap
  root((System Design))
    Data Storage
      Relational DB PostgreSQL MySQL
      NoSQL MongoDB DynamoDB
      Time-Series InfluxDB
      Search Elasticsearch
      Graph Neo4j
    Caching
      In-process cache
      Redis Memcached
      CDN edge cache
    Async Processing
      Message Queues Kafka SQS
      Task Queues Celery
      Event Streaming
    Communication
      REST HTTP
      gRPC Protobuf
      WebSockets
      SSE
    Infrastructure
      Load Balancers
      API Gateways
      Service Mesh
      CDN
    Reliability
      Circuit Breakers
      Rate Limiting
      Dead Letter Queues
      Retries with Backoff

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Interview tip: When you draw a component on the whiteboard, be ready to go one level deeper on any of it. If you write "Kafka" — know partitions, consumer groups, delivery guarantees, and when you'd use SQS instead.