Add one person to a team of ten and you add ten new coordination paths. Add five and you add fifty-five. In a group of n people where every pair coordinates directly, the path count is n(n−1)/2 — at fifteen people, 105 paths; at twenty, 190.
In practice these paths show up as alignment meetings, Slack threads that branch into six sub-threads, and decisions that take a week because everyone needs to be in the room. None of this ships. It is the overhead of staying synchronised, and it scales faster than the team.
The simulator below shows what happens to path count as headcount grows — and what changes when the same people are organised into services.
Organising for flow
Grouping people into services changes the topology. Within a service, coordination is dense and fast — everyone shares context, the board is visible to the whole team, decisions happen without scheduling a meeting. Between services, coordination narrows to a defined interface: a request queue with an explicit SLA.
The same headcount generates a fraction of the coordination overhead. The paths that remain are either internal (cheap, because team members share context already) or external (legible, because they cross a defined boundary with an explicit owner).
Conway’s Law describes this mechanism: the communication structure of an organisation tends to shape the architecture of what it builds. A set of services with narrow, defined external interfaces tends to produce software with narrow, defined APIs. The team topology you design is the system architecture you will get.
Takeaways
- — Path count grows as n(n−1)/2. Adding people to a flat structure multiplies coordination overhead faster than it adds capacity.
- — Dense internal communication is an asset. Within a service, shared context speeds decisions. Cross-team coordination without defined interfaces is what drives overhead.
- — Narrow inter-service interfaces reduce overhead. Request queues and explicit SLAs make cross-team dependencies legible and limit unplanned coordination work.
- — Communication structure shapes system structure. Conway’s Law operates whether you plan for it or not. Design the communication topology you want to see in the product.