Senior Engineer - VCL Compiler

Fastly helps people stay better connected with the things they love. Fastly’s edge cloud platform enables customers to create great digital experiences quickly, securely, and reliably by processing, serving, and securing our customers’ applications as close to their end-users as possible — at the edge of the Internet. The platform is designed to take advantage of the modern internet, to be programmable, and to support agile software development. Fastly’s customers include many of the world’s most prominent companies, including GitHub, Yelp, Paramount, and JetBlue. We're building a more trustworthy Internet. Come join us. Posting Open Date: Aug. 4, 2026 Anticipated Posting Close Date*: Aug. 17, 2026 *Job posting may close early due to the volume of applicants. Sr Software 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. What You'll Do: 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 What We're Looking For: 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 We’ll be super impressed if you have experience in any of these: 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 Work Hours: 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. Work Location(s) & Travel Requirements: The preferred locations for this position are: New York, NY Denver, CO San Francisco, CA Fastly currently embraces a largely hybrid model for most roles which allows employees flexibility to split their time between the office and home. There is a strong preference for Hybrid near a local office. However, we may be willing to consider exceptionally qualified remote candidates within the US. This position may require travel as required by your role or requested by your manager. Pursuant to the San Francisco Fair Chance Ordinance and the Los Angeles Fair Chance Initiative for Hiring Ordinance, we will consider for employment qualified applicants with arrest and conviction records. Salary: The estimated salary r…