System Design Canvases
Printable practice resource: System Design Canvases.
How to use this resource
Use the canvas before each 45-minute system design mock. Fill it in from left to right, then use the last five minutes to state risks and next steps.
Use two passes. The first creates a coherent minimum design; the second attacks the constraint most likely to break it. Do not spread time evenly across boxes.
Pass one — establish the system
| Area | Questions and notes |
|---|---|
| Outcome and users | Who acts, what must happen, and what is explicitly outside scope? |
| Critical flows | What is the most important write, read, and asynchronous path? |
| Contract | What APIs, events, errors, and idempotency rules are visible? |
| Data ownership | Which system owns each fact, and what consistency is required? |
| Workload | What are the volume, latency, fan-out, growth, and skew assumptions? |
| Minimum architecture | What is the simplest path that satisfies the prioritized constraints? |
Pass two — make it operable
| Area | Questions and notes |
|---|---|
| Failure | Where can work be lost, duplicated, delayed, corrupted, or amplified? |
| Overload | What is bounded, rejected, queued, shed, or degraded? |
| Observability | Which signal triggers which operator or automated decision? |
| Security and privacy | Who may perform each action, and where does sensitive data travel? |
| Rollout and recovery | How is compatibility preserved, change verified, and failure reversed? |
| Cost and evolution | What dominates cost now, and which threshold changes the design? |
Suggested 45-minute allocation
Use 5 minutes for framing, 8 for contracts and estimates, 15 for the critical path, 10 for failure and operations, and 7 for trade-offs and summary. Adjust when the interviewer redirects; the allocation is a control loop, not a script.
Finish with a recommendation, the largest residual risk, and the next piece of evidence you would obtain. Pair this canvas with Appendix D — System Design Formula Sheet when estimates drive the architecture.