Senior Backend Software Engineer (APIs)
Fastly
San Francisco, United States Posted September 19, 2026
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Salary Range
$181,220 - $217,464
Job Description
Join Fastly, a leading edge cloud platform, as a Senior Backend Software Engineer. In this role, you will design, ship, and own public-facing APIs and backend services in Go. You will collaborate with frontend engineers, product managers, and security researchers to deliver an exceptional customer experience. You will also mentor and grow other engineers on the team and participate in an on-call rotation. Fastly offers a range of benefits, including generous parental leave, health and wellness coverage, retirement plans, and opportunities for learning and development.
- Design, ship, and own public-facing APIs and backend services in Go, from technical proposal & design docs through implementation, testing, and production rollout.
- Collaborate with internal platform teams, product managers, and stakeholders across the organization to understand their needs and deliver impactful solutions.
- Mentor and grow other engineers on the team through code review, pairing, and technical leadership.
- Coding agents as a daily driver, not reluctantly. This team uses them heavily
- 5+ years shipping production Go as your primary language
- 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
- 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
- Testing and observability as subtraction, not addition. You can name a metric you added that paid off — and one you'd delete now
- Hands-on experience designing and building reliable, large-scale backend systems - most Senior Engineers at Fastly have at least 5 years of relevant experience
- 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
- This position will require you to be available during core business hours (Pacific Time) and occasional nights and weekends as required for on call support
- Built or operated security products (WAF, bot, DDoS, app security)
- Working knowledge of auth at API scale (RBAC, OAuth, JWT, SAML)
Required Skills
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