developer-apis enterprise-software telephony
San Francisco, CA

Principal Engineer - Core Services


Twilio’s platform enables businesses to seamlessly integrate modern communications into their applications. From Uber’s anonymous driver communications, to AirBnB’s host identity verification, to eHarmony's connecting matches over the phone, businesses make their communications more relevant and compelling using Twilio. All of these use cases are enabled via simple cloud APIs with on-demand global reach.

To achieve this scale, you will be building a complex distributed platform and solve problems with availability, throughput, latency as well as real-time considerations. 

Phone Numbers systems are at the core of Twilio's services. They are in the critical path of every Twilio Call or SMS and more importantly they enable our customers to scale their business globally by communicating with their customers all over the world.

Getting reliable Phone Numbers in an ever growing list of countries is the highest factor of growth for the whole company.

About the job:

  • Develop low latency, highly available, globally distributed services in the flight path of every Voice and SMS message.
  • Create REST APIs for customers to Search, Buy and Configure millions of phone numbers across 100+ countries and growing.
  • Design and build tools to Add, Manage and Tests phone number inventory.
  • Work in a small, empowered team. Move fast - ship to prod multiple times in a 1 week sprint.
  • Own and operate production services in AWS cloud infrastructure using the latest tools, like Datadog, Rollbar, Lightstep.
  • Full stack exposure, from UI to database. Java, Python, MySQL, Php, Nginx, all on AWS.


  • Collaborate with Peers, Product Managers, Architects and Engineering leaders to define, architect and build new customer-facing features.
  • Tackle some of the most challenging problems you can face developing highly available services in a distributed cloud environment that needs to scale.
  • Break down requirements, estimate tasks and plan work accurately. Definition of done is Production.
  • Release, monitor, and maintain features in a responsible, reliable way.
  • Drive quality by writing unit, functional, load, performance and resiliency tests.
  • Support development operations, building, releasing and assisting with team on-call.
  • Employ Agile methodologies to continuously deliver value to customers.
  • Leadership is a behavioral trait, not a title, including leading architecture, design and code reviews as well as mentoring other engineers.


  • Minimum 8+ years experience building complex distributed systems across concerns of reliability, high-availability, performance, scalability, capacity planning, business continuity and automation.
  • Extensive experience developing, deploying, scaling production backend systems in Java.
  • Experience with scaling data tiers employing a variety of SQL/NoSQL database and caching technologies.
  • Expert level understanding of object oriented design and data modeling.
  • Experience with a Cloud Service Provider, such as AWS, GCP or Azure.
  • True Agile mindset (XP preferred).

Bonus points:

  • Experience with a scalable data pipeline, preferably with Kafka, Kinesis, Spark is a plus.
  • Ideally, you have experience in a highly-available, uptime-critical production environment.
  • Experience working in an environment where you have ownership of in many technical areas

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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