Principal, Software Engineer (L5)

Who we are At Twilio, we’re shaping the future of communications, all from the comfort of our homes. We deliver innovative solutions to hundreds of thousands of businesses and empower millions of developers worldwide to craft personalized customer experiences. Our dedication to remote-first work , and strong culture of connection and global inclusion means that no matter your location, you’re part of a vibrant team with diverse experiences making a global impact each day. As we continue to revolutionize how the world interacts, we’re acquiring new skills and experiences that make work feel truly rewarding. Your career at Twilio is in your hands. . Hiring and how we work We use Artificial Intelligence (AI) to help make our hiring process efficient. That said, every hiring decision is made by real Twilions! Also, while we are a remote-first company, you may be asked to report in person on an ad-hoc basis for team gatherings, functional off-sites or customer meetings. . See yourself at Twilio Join the team as Twilio’s next Principal Software Engineer. About the job This position is needed to raise the technical depth of the systems that continuously test, measure, and assure the quality of Twilio's global carrier connections, and the operational platforms that Super Network's operations depend on. Every call and message Twilio makes crosses a carrier network we don't control. This team is how we know those connections are healthy. We monitor and test them continuously, worldwide, for both voice and messaging reliability, and we build what our operations teams use to act on what we find. Increasingly that means LLM agents troubleshooting carrier problems without a human involved — and that's the part we most want to push further. Responsibilities In this role, you’ll: Design and deliver major components of Twilio's carrier test and observability platform, covering active voice and messaging testing, quality scoring, and global test coverage. Build high-throughput data and alerting systems that turn the data into signals operations teams can act on without drowning in noise. Extend and harden our production LLM systems for automated carrier troubleshooting — expanding the classes of issue they resolve without human intervention, and owning the evaluation, observability, and guardrails that make autonomous action safe. Diagnose cross-boundary failures where test results, carrier behavior, and platform telemetry disagree, and establish the observability needed to tell those cases apart. Contribute to technical design and review across the team, mentor engineers, and help shape written standards that outlast any single project. Qualifications Twilio values diverse experiences from all kinds of industries, and we encourage everyone who meets the required qualifications to apply. If your career is just starting or hasn't followed a traditional path, don't let that stop you from considering Twilio. We are always looking for people who will bring something new to the table! *Required: 12+ years of software engineering experience, including significant time at staff or principal level working on systems at large scale. Deep expertise designing, operating, and debugging distributed systems that ingest and process high-volume time-series or event data in production, including alerting, anomaly detection, and failure isolation. Hands-on experience taking LLM-based systems to production and keeping them there: context and tool design, evaluation against real outcomes, cost and latency management, and the guardrails required when model output triggers real actions rather than just producing text. Strong proficiency in at least one backend language used at scale (Java, Go, Scala, or similar) and fluency with event streaming and cloud infrastructure (Kafka, AWS, Kubernetes). Ability to communicate complex technical trade-offs clearly in writing and to influence peers through des