the mistake to avoid
most org charts classify teams by function — backend, frontend, data, mobile, sre. that's a job-title taxonomy. it tells you what people do at a desk, not how value flows through the company. team topologies classifies by purpose: what is this team for, and who depends on it to do their work?
four types, each with a job. every team in the org should map cleanly to one of them. if it maps to two, it's probably two teams in a trenchcoat — and that's lesson six.
the four types
- stream-aligned the default. owns a single, valuable flow of work end-to-end — a product area, a user journey, a customer segment. ships to users directly. most teams in most orgs should be this. if you don't know what a team is, assume stream-aligned.
- platform serves other teams as customers. builds an internal product — ci/cd, observability, a container platform, an auth service — that stream-aligned teams consume without raising tickets. the measure of a good platform team is how often its customers choose to use it vs route around it.
- enabling a temporary coaching team. shows up, closes a capability gap in a stream-aligned team (cloud adoption, security practices, a new testing discipline), then leaves. if an enabling team becomes permanent, it's misclassified — either they're platform, or they're stream-aligned, or they shouldn't exist.
- complicated-subsystem owns something whose mastery is so specialised the rest of the org can't reasonably hold it. pricing engines, video codecs, simulation models, tricky numerical libraries. small, insulated, and provides its output as a crisp interface others can use without understanding the internals.
try it
classify these teams
eight teams from a fictional company. click a team, then click the type you think it belongs to. check your answers when you've assigned all eight.
- owns everything the customer touches during checkout — cart, address, payment capture, confirmation emails. ships behind a flag weekly. → stream-aligned one end-to-end slice of customer value, owned turn-by-turn.
- runs the internal kubernetes platform. other teams push yaml; they get logs, secrets, traffic shifting, rollbacks out of the box. → platform a self-service product with a paying (internal) customer base.
- three people with phds who maintain the real-time bid-optimization engine. it's a dense body of math the rest of the org can't reason about. → complicated-subsystem deep specialism where replicating the knowledge would be wasteful or impossible.
- a four-person team embedded for one quarter with the mobile squad to teach them trunk-based development and pipeline design, then rotates out. → enabling short-lived coaching engagement, not a permanent capability provider.
- owns the new-user onboarding flow across web and mobile. a/b tests weekly, activates or deactivates variants based on 14-day retention. → stream-aligned a coherent slice of the product with its own metrics and flow of change.
- builds the internal search service. teams subscribe to indexing pipelines, get a query api, get dashboards. versioned quarterly. → platform shared capability consumed self-service with a product mindset.
- two specialists who train and tune the fraud-scoring models. the rest of the org gets a score; they don't see the model. → complicated-subsystem the knowledge to build and tune the models isn't worth replicating elsewhere.
- three accessibility experts brought in for a six-week engagement with the checkout team to get them past wcag 2.1 aa before a legal deadline. → enabling time-boxed, goal-bound coaching. when the gap is closed, they leave.
the cost of getting it wrong
misclassification is the origin of most team-dysfunction complaints. a platform team that behaves as stream-aligned ends up owning features nobody else can work on. a stream-aligned team that's secretly a platform team never ships anything because every other team keeps interrupting it. complicated-subsystem teams that forget to publish an interface become oracles — the org can't ship without asking them a question.
the four types are simple, but the discipline of applying them cleanly is where most of the value lives. the rest of the course is about that discipline.
next: the three interaction modes, and why picking the wrong one is so expensive.