Software architecture · Case studies
Case studies: architecture decisions in real applications
The modules teach one idea at a time. Real decisions mix them: a database choice turns out to be a compliance question, a cost problem turns out to be an architecture style problem, a reliability failure turns out to be a governance failure. Each case study follows one application through a decision from start to finish, and links back to the modules it draws on. 12 of 12 are live.
How each case is told
| Section | What it covers |
|---|---|
| Situation and drivers | The application, its scale and constraints, and the architecture characteristics that mattered most |
| Options and decision | The alternatives compared, and the decision written as an ADR (format on the Templates page) |
| How it works | An animation of the mechanism that decided the case |
| Numbers and outcome | Costs, risks and what actually happened |
| Lessons and your turn | What carries over to other systems, interview answers, an exercise and a quiz |
Real cases and invented companiesA real case is analysed from the company's own public engineering write-up, linked under Sources; figures that aren't in the source are marked as illustrative. An invented company is a realistic composite, used where the story needs internal detail (an ADR, a review, a bill) that no one publishes; the laws, prices and products it mentions are real.
Governance and decisions
C01Invented companyAn ADR that avoided a lock-in trapA payments SaaS expanding to India nearly picked a database that would have broken data residency.C02Invented companyReplacing a review board that slowed everyone downA 300-engineer company swaps a monthly approval board for the advice process.C03Real caseSpotify: Backstage and golden pathsPlatform engineering for thousands of services: a developer portal and paved roads.
Cost and economics
C04Invented companyFrom zero to a million users: one startup's cloud billEstimating cost at design time, the traps at 100,000 users, and moving off serverless at scale.C05Real casePrime Video: from serverless to one processA monitoring service that cut infrastructure cost by over 90% by collapsing its distributed parts.C06Real case37signals leaves the cloudBuying servers instead of renting: capex, opex and what the numbers turned out to be.
Structure and evolution
C07Real caseSegment: back from microservicesOver a hundred destination services merged back into one, and why.C08Real caseShopify: the modular monolithKeeping one codebase and enforcing boundaries inside it with tooling.C09Real caseUber: domain-oriented microservicesGrouping thousands of microservices into domains, layers and gateways.
Reliability and compliance
C10Real caseGitLab's 2017 database outageAn accidental deletion, five backup methods that didn't work, and six hours of lost data.C11Real caseNetflix: active-active across regionsServing from several regions at once so a whole region can be evacuated.C12Invented companyHealth data across India and the USData residency, HIPAA and disaster recovery for a telehealth product in two countries.