System design
Show where System design affected a real decision in the project. Include the implementation, constraint, test or measurement that makes the skill verifiable.
CAREER PROJECT · Advanced · 2 weekends
Feature Flag Service
Create flags, environments, targeting rules, audit history and a tiny client SDK.
System designAPIsCachingSDKsAuditability
WHAT THIS PROJECT PROVES
Make the engineering visible.
This brief is designed as portfolio evidence for a Software Engineer path. The goal is not to claim a hiring outcome; it is to make your implementation, judgment and tradeoffs easier to inspect.
APIs
Show where APIs affected a real decision in the project. Include the implementation, constraint, test or measurement that makes the skill verifiable.
Caching
Show where Caching affected a real decision in the project. Include the implementation, constraint, test or measurement that makes the skill verifiable.
SDKs
Show where SDKs affected a real decision in the project. Include the implementation, constraint, test or measurement that makes the skill verifiable.
Auditability
Show where Auditability affected a real decision in the project. Include the implementation, constraint, test or measurement that makes the skill verifiable.
BUILD PLAN
Finish the core before expanding the scope.
Use this as a project sequence, not a rigid tutorial. Your stack can change; the evidence should still show what you built, why you built it that way and how you know it works.
Define the scope and success criteria
Turn the brief into a small finishable system. Decide what the core Feature Flag Service must do, what you will deliberately leave out, and how you will show that it works.
Build the core workflow
Create flags, environments, targeting rules, audit history and a tiny client SDK. Keep the first pass focused on the main user or system flow before adding stretch features.
Add engineering proof
Create admin ui and flag api. Document the decisions, failure states, tests, performance, security or operational tradeoffs that matter for this project.
Ship and package the evidence
Publish the strongest artifacts, including client sdk, audit log, architecture notes. Make it easy for a reviewer to understand the problem, architecture, tradeoffs and what you personally implemented.
PORTFOLIO PROOF CHECKLIST
Leave artifacts a reviewer can inspect.
A strong project page should make it possible to understand the system without guessing what you personally built.
01
Admin UI
02
Flag API
03
Client SDK
04
Audit log
05
Architecture notes
06
A concise README explaining the problem, architecture and tradeoffs
07
A working demo, API example or reproducible run path
08
Evidence of testing, monitoring, performance, accessibility or reliability where relevant
RESUME / PORTFOLIO FRAMING
Describe what you actually did.
Designed a feature-flag platform with targeting rules, low-latency evaluation, audit history and a client SDK.
Use this as a starting structure, then replace it with your real implementation details, metrics and constraints. Do not claim outcomes you did not measure.
INTERVIEW TALKING POINTS
Be ready to defend the decisions.
These prompts turn the project from a repository link into a technical conversation about judgment, tradeoffs and evidence.
Why did you choose your approach to System design, and what alternative did you reject?
Answer with details from your implementation. Prefer concrete constraints, measurements and alternatives over generic best practices.
Where could Feature Flag Service fail under real usage, and how would you detect or recover from that failure?
Answer with details from your implementation. Prefer concrete constraints, measurements and alternatives over generic best practices.
How did APIs affect the rest of the design?
Answer with details from your implementation. Prefer concrete constraints, measurements and alternatives over generic best practices.
What did you measure or test to prove Auditability instead of only claiming it?
Answer with details from your implementation. Prefer concrete constraints, measurements and alternatives over generic best practices.
If you had one more week, what would you improve first and why?
Answer with details from your implementation. Prefer concrete constraints, measurements and alternatives over generic best practices.
STRETCH GOALS
Go deeper only after the core is solid.
Streaming updates
Add it only if it strengthens the engineering story instead of delaying a finished, deployable core.
Percentage rollout
Add it only if it strengthens the engineering story instead of delaying a finished, deployable core.
Multi-region design
Add it only if it strengthens the engineering story instead of delaying a finished, deployable core.
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