developer-apis enterprise-software telephony
San Francisco, CA

Principal Software Engineer - Runtime


Twilio is more than just an API… it’s a communications platform that empowers developers to build some of the most innovative apps in the world.

The Runtime Team's mission is to help our customers get to production as fast as possible leveraging the Twilio Cloud and all it has to offer.  Some of the products this team is responsible for include:

  • Twilio Functions and Assets:  Our lambda and static content hosting service.  This product helps our customers delpy directly into the Twilio cloud, saving them the need to find a place to productionize and scale their code.
  • Twilio Debugger:  The debugger gives our customers the ability to quickly diagnose problems in their code or across our communications cloud.
  • Twilio API Explorer:  The API explorer allows customers to learn the API inside the Web Console.  It can also generate code in the language of their choice that they can just drop into their code base. 

The users of the Runtime platform are varied - some are just learning about Twilio and others are experts in Serverless design looking for the most reliable way to deploy their communications software.  Additionally, the Runtime platform serves internal Twilio products adding functionality. It is a foundational piece of tech for all of Twilio.

About the Job:

The Runtime team is looking for a principal engineer to work closely with Runtime’s product manager and engineering manager to craft and implement a roadmap for the future of Serverless.  This role will help drive the future direction of this product and then build it (and the team around it) over a 2-3 year time horizon.  

It’s expected that this person has a strong understanding of the state of Serverless in the industry and also has strong feelings of where it will go.  In this role, you get to build the future of Serverless at a leading developer focused company.

The ideal candidate should be able to nimbly jump between languages and ramp up quickly on a complex large architecture that spans multiple services.

The role will also be responsible for the mentorship and growth of engineers that range from Senior Engineers to Junior Apprentices.  They should be able to design systems and leave the implementation details to their engineers — letting junior engineers grow comfortable with ownership of various products

This person should be excited about new serverless technologies and be innately curious about what the latest innovations in the space are.

At Twilio, there is an expectation that engineering leaders all code, deploy and exhibit full ownership of their services.  


  • Passionate and well versed in modern Serverless programming.  You take gleeful delight in chopping up traditional software into discrete functions.  (And can’t wait to build new systems that make it easier for other developers to do the same!)
  • Comfortable with functional and OO programming - the vast majority of our services are in Java and Scala.  We are also active developers in Node, Python and older legacy systems in PHP.
  • Architects systems with the mindset of multiple orders of magnitude growth in a 2 year time horizon.
  • Able to reach buy-in on complex technical decisions.
  • Evangelizes a serverless platform both inside and outside the company.  You are comfortable being the engineering face of Serverless initiatives.
  • Work closely with product management & infrastructure engineering to define, architect, and build new services.
  • Provide technical mentoring and guidance to team members as they implement new services.
  • Apply a metrics driven approach to product operational maintainability and success. We are building services with expectations of multiple 9s SLAs.


  • Degrees are nice but experience is what we look for.  Looking for 12+ years experience in the industry with a significant portion of it in the Serverless space.
  • Strong development skills in functional and OO programming.  We are a big Scala and Java shop.  This team also uses Node and Python extensively.
  • Built high throughput, highly available services with an eye for operational stability.
  • Comfortable working on developer-first products (notably with experience in API design and the developer mindset)
  • Background in HTTP, networking, and security.
  • Background in cloud based providers (AWS, Azure, GCP, and others) and their Lambda products.
  • Experience with modern Javascript frameworks: React/Redux, ES6, EmberJS, Angular, Polymer.  

Bonus points:

  • You know what it means to be a defensive programmer.
  • You think of ways to parallelize complex long tasks.
  • You feel that functions and lambdas are the future of development.
  • You are developer who wants to work at a developer-focused company.
  • You have seen systems break when deployed at scale and learned valuable lessons from those experiences.


About us:

Twilio's mission is to fuel the future of communications. Developers and businesses use Twilio to make communications relevant and contextual by embedding messaging, voice and video capabilities directly into their software applications. Founded in 2008, Twilio has over 650 employees, with headquarters in San Francisco and other offices in Bogotá, Dublin, Hong Kong, London, Madrid, Mountain View, Munich, New York City, Singapore and Tallinn.

Twilio is proud to be an equal opportunity workplace and is an affirmative action employer. We are committed to equal opportunity regardless of race, color, ancestry, religion, gender, gender identity, parental or pregnancy status, national origin, sexual orientation, age, citizenship, marital status, disability, or Veteran status and operate in compliance with the San Francisco Fair Chance Ordinance.

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