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.

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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.

• 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.

• 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

• 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

• 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.

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.

We care about you. Fastly works hard to create a positive environment for our employees, and we think your life outside of work is important too. We support our teams with great benefits that start on the first day of your employment with Fastly. Curious about our offerings? 

We offer a comprehensive benefits package including medical, dental, and vision insurance. Family planning, mental health support along with Employee Assistance Program, Insurance (Life, Disability, and Accident), a Flexible Vacation policy and up to 18 days of accrued paid sick leave are there to help support our employees. We also offer 401(k) (including company match) and an Employee Stock Purchase Program. For 2026, we offer 11 paid local holidays, 12 paid company wellness days.

• We have a huge impact. Fastly is a small company with a big reach. Not only do our customers have a tremendous user base, but we also support a growing number of open source projects and initiatives. Outside of code, employees are encouraged to share causes close to their heart with others so we can help lend a supportive hand.
• We value diversity. Growing and maintaining our inclusive and diverse team matters to us. We are committed to being a company where our employees feel comfortable bringing their authentic selves to work and have the ability to be successful -- every day.
• We are passionate. Fastly is chock full of passionate people and we’re not ‘one size fits all’. Fastly employs authors, pilots, skiers, parents (of humans and animals), makeup geeks, coffee connoisseurs, and more. We love employees for who they are and what they are passionate about.

We’re always looking for humble, sharp, and creative folks to join the Fastly team. If you think you might be a fit please apply! A fully completed application and resume or CV are required when applying.

All job applications must be submitted through our official careers site at www.fastly.com/about/careers. We will never request sensitive information, such as your Social Security number, bank account or credit card information during the application process. All official communication will come from an @fastly.com or @recruiting.fastly.com email address.