At QCon London 2025, Tom Akehurst, creator of WireMock, addressed the challenges of achieving developer autonomy in large-scale microservices environments. In his talk, “Scaling API Independence: Mocking, Contract Testing & Observability in Large Microservices Environments,” Akehurst outlined a strategy combining mocking, contract testing, and traffic observation to enable fast-flowing development and testing.
While microservices promise faster deployments and team autonomy, Akehurst argued that developers often face delays due to API dependencies, broken sandboxes, and complex testing environments. He emphasized that maintaining realistic and reliable mocks is a significant challenge at the scale of thousands of internal APIs. He noted that teams often find themselves blocked, waiting for others to complete their APIs, or spending excessive time debugging integration issues.
The presentation explored how to move beyond basic API mocking to more sophisticated, stateful mocks, acknowledging the complexity but stressing its importance in modeling real-world interactions. Akehurst positioned WireMock as part of a broader solution architecture, highlighting the need to combine API simulation with observability and validation. He emphasized that effective API simulation is not just about returning canned responses but about accurately reflecting the behavior of the real API, including its various states and transitions.
Akehurst also discussed:
- Contract Testing at Scale: Using specifications to align consumer-provider expectations. He explained how contracts can define the expected interactions between a consumer and a provider, ensuring that both sides adhere to the agreed-upon interface. This becomes crucial in large-scale systems where changes in one service can have ripple effects on many others.
- Observability Integration: Leveraging real traffic captures to generate realistic mocks and detect mismatches between contracts and reality. Akehurst highlighted the importance of observing how APIs are being used in production. This allows for the creation of more accurate mocks and the detection of any deviations from the defined contracts. Tools like eBPF and service mesh can significantly affect this process.
- Productivity through AI: Exploring how AI and large language models (LLMs) can enhance API simulations. Akehurst suggested that AI can automatically generate and refine mock data, reducing the manual effort to maintain mocks. This can significantly improve developer productivity and accelerate the development cycle.
Akehurst emphasized that true independence in microservices doesn’t mean isolation. By combining API simulation with observability and validation, organizations can maintain team autonomy while ensuring integration confidence. He argued that these techniques are essential for managing the complexity of modern microservices architectures and enabling teams to deliver value quickly and reliably.
