API Documentation
Docs + Word14 pages
Free
- Type
- Document
- Price
- Free
- Pages
- 8 · US Letter
- Style
- Modern
- Difficulty
- Beginner
- Updated
- November 1, 2026
Every page (8)
Overview
Architecture knowledge lives in a few heads until a new engineer joins or a reviewer asks why a choice was made. This template documents a system in C4 order, from the context around it to its containers and components, then adds the quality attributes it must meet, the decisions behind it and the risks that remain.
The sample describes Quillon Cloud, a document signing platform with 14 services in two regions, 99.95% availability and a p95 latency of 280 ms. It includes a layered diagram, an API reference page, a quality checklist, a storage decision with rejected options and a risk register. Replace the services, owners, targets and decisions with your own, and set the last-reviewed date.
Useful for
- A tech lead onboarding new engineers with a single document that explains the system and its owners
- An architect recording a storage or hosting decision with the options rejected and the reasons
- A platform team preparing for a design review with quality targets, evidence and open risks
What's included
- Cover and a context page covering scope, users, external systems and design constraints
- Container page with a layered architecture diagram and a step-by-step request flow
- Component reference page for one API operation with parameters and example request and response
- Quality attribute checklist with owners and due dates, and a pre-release review list
- Decision page comparing three options against criteria with a recommendation and rejected options
- Risk register with likelihood and impact ratings, owners and responses, plus a Make it yours guide
How to use it
- 1
Click Make a copy in Google Docs, then confirm on the Google page. The copy is saved to your own Google Drive.
- 2
Replace the context page with your own users, upstream and downstream systems, then list your real services with an owner team, language and datastore.
- 3
Rewrite the quality attributes using the service level objectives you actually run, with the evidence for each, and keep the decisions someone new might reverse.
- 4
Update the risk register, set the last-reviewed date on the cover and name who will review it next.
- 5
Delete the Make it yours guide page, then share the document with your team or present it in a review.
What you need
Requirements
- A Google account with access to Google Drive
Works with
- Google Docs
- Microsoft Word (download the .docx)
Questions
What are the C4 levels?
C4 describes software at four levels: context, containers, components and code. This template covers the first three and adds quality attributes, decisions and risks.
Are Quillon Cloud and its figures real?
No. Quillon Cloud, its teams, services and every figure are fictional sample data. Replace them with your own system details before sharing.
How often should the document be reviewed?
Review it at least every six months and after any major change. Set the last-reviewed date and the next reviewer so readers can tell whether it still matches production.
- #software-architecture
- #c4-model
- #architecture-document
- #system-design
- #tech-lead
- #developer-workflows
- #google-docs
- #adr
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