Senior Engineer (VCL Compiler)

• We are looking for a Compiler Engineer to join our Core Platform team to help shape, scale, and maintain the VCL Compiler (VCC) and Varnish Configuration Language (VCL). VCL is at the heart of how our customers configure and customize their edge logic at scale
• In this role, you will be responsible for evolving the language design, refactoring compiler architecture, and ensuring the absolute stability of a codebase that processes billions of requests per second
• You will balance building innovative language features with the meticulous, detail-oriented work of maintaining backward compatibility, writing robust test suites, and optimizing our C-based code generation pipeline
• Design and implement VCL language extensions, syntax updates, and new compiler features
• Parsing and AST rework to improve long-term maintainability of the compiler
• Refactor and modularize the existing compiler codebase to reduce complexity and improve stability
• Own the testing and validation pipeline to ensure compiler changes don’t break existing customer code
• Collaborate with cross-functional teams to align on architecture and technical direction
• Write clear technical documentation for internal teams and external users
• This position will require you to be available during core business hours. It may also require occasional nights and weekends as necessary to support any on-call coverage

Benefits

• Parental support and beyond: We support our families by offering generous time off for parental leave. And beyond that, we work hard to build a culture that allows for all employees to have the life outside work that they desire year round.
• Health and wellness:
  Your well-being matters here. Our health plans offer a variety of options, including full medical, dental, and vision coverage, short- and long-term disability insurance, mental health resources, and more.
• Invest in your future:
  We offer 401(k)/retirement plans, employee stock purchasing plans (ESPP), and reimbursements for learning and development programs — so we can support your ongoing growth and success.
• Keep learning and growing: Helping people go further means nurturing their talent. Through annual reimbursements for employee learning activities, regular hangouts and advice from our Senior Staff, talks from industry leaders, and cultural events — we offer tons of opportunities for people to learn. And we’re always looking to grow as a company, too: we collect employee engagement and experience data annually and leverage our Employee Experience Champion Network to understand employee feedback, so we can keep improving.- Significant production experience writing C, with knowledge of POSIX/Linux environments
• Significant domain-relevant engineering experience - Most Senior Engineers at Fastly have at least 5 years of related experience
• Good written communication skills, with the ability to produce clear technical documentation
• Track record of comprehensive testing practices, CI/CD, and treating the build pipeline as production infrastructure
• Solid understanding of compiler internals: parsing, AST design, intermediate representations, code generation
• Experience simplifying and refactoring established codebases while maintaining backward compatibility
• A collaborative mindset with experience working across cross-functional teams
• Previous Fastly engineering experience
• Contributions to open source compiler or language projects
• Familiarity with Varnish, VCL, or CDN/edge computing infrastructure
• Background in domain-specific language (DSL) design- Anticipated Posting Close Date: Aug. 17, 2026