System Design Projects (Build It, Not Just Diagram It)

Most system design prep stops at the whiteboard. These senior projects make you actually build the thing - zero-downtime migrations, sagas, rate limiters, multi-tenant isolation, blue-green deploys - in a live cloud workspace, so you can speak to the trade-offs because you lived them.

Why building beats memorizing diagrams

System design interviews fail people who have only read about it. You can recite "use a message queue" but stall when asked what happens when the consumer dies mid-batch - because you have never had one die on you. These make you build the thing and hit the failure mode, so your answers come from memory, not theory.

22 projects to start with

Build an End-to-End RAG PipelineAI/ML · Senior Build an LLM Evaluation Harness (Golden Set)AI/ML · Senior Route LLM Requests to Cheaper ModelsAI/ML · Senior Build a Tool-Calling Agent LoopAI/ML · Senior Add a NOT NULL Column With a Zero-Downtime BackfillBackend · Senior Refactor Globals Into Dependency InjectionBackend · Senior Design a URL Shortener (System Design)Backend · Senior Design a Rate Limiter (Token Bucket)Backend · Senior Build a Kimball Star SchemaData · Senior Build an Exactly-Once Kafka PipelineData · Senior Switch Batch ETL to Streaming on AWS KinesisData · Senior Ship a Zero-Downtime Blue-Green DeployDevOps · Senior Package an App as a Helm ChartDevOps · Senior Move Secrets Into HashiCorp VaultDevOps · Senior Deploy a React App Globally With AWS CloudFrontFullstack · Senior Replace LIKE Search With Postgres Full-Text SearchFullstack · Senior Lock Down a Namespace With a NetworkPolicyKubernetes · Senior Write a Helm Chart for a Multi-Service AppKubernetes · Senior Run a Multi-Container Pod with a SidecarKubernetes · Senior Spread Replicas with Pod Anti-AffinityKubernetes · Senior Secure a Webhook Endpoint (HMAC + Replay)Security · Senior Move JWT to httpOnly Cookies (XSS + CSRF)Security · Senior

Build it, then you can talk about it

Afterward you can answer the follow-up that separates senior from mid: not "what would you use" but "what broke when you used it, and what you would change." Zero-downtime migrations where you watched the lock, sagas where you traced the compensating action, rate limiters where you tuned the bucket - lived trade-offs, not whiteboard ones.

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