Senior Engineer - VCL Compiler

About the role

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.

Responsibilities

• 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

Requirements

• Significant domain-relevant engineering experience (most Senior Engineers at Fastly have at least 5 years of related experience)
• Significant production experience writing C, with knowledge of POSIX/Linux environments
• Solid understanding of compiler internals: parsing, AST design, intermediate representations, code generation
• Experience simplifying and refactoring established codebases while maintaining backward compatibility
• Track record of comprehensive testing practices, CI/CD, and treating the build pipeline as production infrastructure
• Good written communication skills, with the ability to produce clear technical documentation
• A collaborative mindset with experience working across cross-functional teams

Nice-to-have Skills

• 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

Schedule

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.

Location

The preferred locations for this position are New York, NY; Denver, CO; or San Francisco, CA. Fastly embraces a largely hybrid model, allowing employees flexibility to split their time between the office and home. There is a strong preference for hybrid near a local office, though exceptionally qualified remote candidates within the US may be considered. This position may require travel as required by your role or requested by your manager.

Pay

The estimated salary range for this position is $181,220 to $217,464. Starting salary may vary based on permissible, non-discriminatory factors such as experience, skills, qualifications, and location. This role may be eligible to participate in Fastly’s equity and discretionary bonus programs.

Benefits

• Comprehensive medical, dental, and vision insurance
• Family planning and mental health support, including Employee Assistance Program
• Life, disability, and accident insurance
• Flexible Vacation policy and up to 18 days of accrued paid sick leave
• 401(k) with company match
• Employee Stock Purchase Program
• 11 paid local holidays and 12 paid company wellness days for 2026