Most discussions about APIs focus on technology choices: REST vs. GraphQL, JSON vs. Protobuf, synchronous vs. asynchronous communication. But the real impact of APIs goes far beyond transport protocols and serialization formats.

APIs define system boundaries. They shape coupling between teams and services, influence scalability and resilience, and determine how complexity spreads through a system. In many modern architectures, the most critical architectural decisions are actually API design decisions.

This talk explores APIs from a software architecture perspective. We will look at how different communication styles create different architectural trade-offs, why poorly designed APIs lead to hidden complexity and cascading failures, and how architectural qualities such as loose coupling, evolvability, and resilience are directly influenced by API design.

Using practical examples and real-world architectural patterns, this session will show why APIs are not just interfaces to your architecture — they are your architecture.