Senior Backend Software Engineer (APIs)

What You'll Do:

• Design, ship, and own public-facing APIs and backend services in Go -from technical proposal & design docs through implementation, testing, and production rollout and on-call support.
• Use AI coding agents as part of your daily workflow.
• Partner with frontend engineers, product managers, and security researchers to ship the customer experience end-to-end.
• Take ambiguous or broadly-scoped problems and turn them into well-defined technical plans that the team can execute on.
• Author design and architectural documents and use them to drive alignment across engineering and product teams
• Collaborate with internal platform teams, product managers, and stakeholders across the organization to understand their needs and deliver impactful solutions
• Consider stability, performance, and scalability in your designs and in the guidance you provide to the team
• Mentor and grow other engineers on the team through code review, pairing, and technical leadership
• Participate in an on-call rotation

What We're Looking For:

• Hands-on experience designing and building reliable, large-scale backend systems - most Senior Engineers at Fastly have at least 5 years of relevant experience
• 5+ years shipping production Go as your primary language.
• 3+ years on public APIs with external consumers. You've shipped a breaking change to customers who'd already integrated against your API. You've written a deprecation notice that actually went out.
• You drive projects, not just tasks. You've owned a multi-week effort end-to-end: design doc through post-launch.
• Good judgement on RESTful API design: resource modeling, versioning, idempotency, error semantics, pagination, OpenAPI. You've made one of these calls wrong in production and remember what it cost to clean up.
• You design for the people downstream of your API. The customer hitting your endpoint at 3am, the support engineer debugging their escalation, the frontend teammate integrating against your contract. You've watched a vague error message of yours confuse someone and changed how you write them since
• Testing and observability as subtraction, not addition. You can name a metric you added that paid off — and one you'd delete now.
• Coding agents as a daily driver, not reluctantly. This team uses them heavily

We’ll be super impressed if you have experience in any of these:

• Built or operated security products (WAF, bot, DDoS, app security).
• Working knowledge of auth at API scale (RBAC, OAuth, JWT, SAML)