Scaling API Independence: Mocking, Contract Testing & Observability in Large Microservices Environments

QCon London 2025

Session APIs

Scaling API Independence: Mocking, Contract Testing & Observability in Large Microservices Environments

Wednesday Apr 9 / 01:35PM BST, Whittle (3rd Fl.)

Abstract

Microservices promise faster deployments and team autonomy. In reality, engineers are often blocked waiting for APIs, dealing with broken sandboxes, or wrangling test environments.

Mocking helps decouple dependencies and teams - but at the scale of 1,000+ internal APIs, maintaining realistic, reliable mocks is a challenge of its own. How do you ensure contract alignment? How do you keep mocks up-to-date without excessive maintenance?

In this talk, we'll explore new ways to combine mocking, contract testing, and traffic observation to support fast-flowing development and testing.

Interview

Building tools to help organisations who depend heavily on APIs develop and test more productively.

I encounter many engineering orgs for whom the promise of microservices - decoupled teams shipping independently - isn't being realized. They're stuck firefighting flakey dependencies and debugging spurious test failures in integrated environments or waiting entire weekends for test runs to complete. In my view this is largely due to some limiting assumptions and beliefs, particularly about mocking/simulation of APIs and how this can be done effectively at scale.

Senior engineers/tech leads, engineering managers, senior QAs, QA managers

With increased confidence that API simulation can be a core pillar of their dev and test strategy, and some new ideas about how to achieve this in complex engineering organizations.

It's hard to bet against AI coding tools at the moment.

In 2013 Damian Conway's presentations were both unforgettable - the showmanship and craft involved in building a latin code interpreter just to present was incredibly impressive, and his second talk on presentation technique is still the one I refer back to the most.

Topics

APIs mocking test automation contract testing Microservices
76% senior dev or higher
1:11 speaker ratio
60+ practitioners

QCon London 2025 is a three day conference for senior software engineers, architects and team leads. An international program committee of working engineers selects every session. Patterns and practices, not products and pitches.

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