B2B software · Europe · Confidential · SaaS
B2B SaaS: API modernisation without breaking hundreds of integrations
A playbook for evolving public APIs: versioning strategy, sunset policy, and how we helped a SaaS vendor reassure enterprise buyers.
Challenge
A decade-old public API was slowing product innovation and worrying enterprise prospects during security reviews.
Outcome
Versioned API, migration window, and partner comms—zero emergency rollbacks in cutover.
Enterprise prospects were asking hard questions about authentication patterns, rate limits, and change management. The product team could not ship net-new capabilities cleanly on top of an under-documented, organically grown API surface.
Strategy
We recommended a new major version rather than silent breaking changes. That sounds obvious, but it requires discipline: parallel operation, clear deprecation timelines, and tooling so integrators could test against a sandbox.
Execution
We mapped existing endpoints to the new design, introduced OpenAPI as the contract source of truth, and built migration guides with request/response diffs. Internal services were refactored behind facades so the core domain did not fork.
Change management
Partner communications went out in waves: design partners first, then general availability with a 9-month sunset for legacy routes. Support metrics and error rates were monitored daily during the first weeks of each wave.
Takeaway
API modernisation is as much product management as engineering. When done well, it unlocks sales cycles and reduces support load—without the reputational damage of a chaotic cutover.
Planning something similar?
This overview reflects delivery patterns we use with teams in b2b software · europe and adjacent sectors—balancing speed, risk, and maintainability. Names and figures are adjusted where needed, but the engineering and collaboration lessons are representative of how we work.
If you are comparing partners for mobile, web, AI, or API work, start with the relevant service page for scope models and FAQs, then use the contact form to share constraints. We will suggest a proportionate next step rather than a one-size-fits-all proposal.