Senior Software Engineer, Backend

Hi, I’m Paul, VP of Engineering at Customer.io . We’re looking for experienced backend engineers who care deeply about reliability, performance, and scalability. You’ll design, build, and evolve the systems that power communication at massive scale - while helping us push the boundaries of what great engineering can look like. About Customer.io Over 9,000 companies - from scrappy startups to global brands - use our platform to send billions of emails, push notifications, in-app messages, and SMS every day. Customer.io powers automated communication that people actually want to receive. We help teams send smarter, more relevant messages using real-time behavioral data. Under the hood: Go, React, Ember and AI help us ship fast and scale with confidence. What We Value Ownership You own problems end to end. You move fast, act like an owner, and thrive in ambiguity. You've led complex projects before, whether officially or not, and you're ready to do it again. Engineers with product taste You think like a user, not just an engineer. You care how your systems power real customer value - and how to make them better. A healthy skepticism for “the way things are done.” You bring rigor and creativity. Best practices matter - but never more than forward motion. What You’ll Do • Design and build distributed systems in Go that help customers send timely, relevant messages at scale • Collaborate across teams to debug issues and deliver reliable solutions • Own problems end to end - from architecture and schema design to testing, deployment, and monitoring • Participate in an on-call rotation as required, supporting the reliability of the systems you build • Share knowledge and raise the bar through sharing your progress publicly with short videos, thoughtful writing, and mentorship • Use AI agents to make multi-file changes by scoping the work, writing the prompt, and verifying the output What we're looking for • 7+ years of experience building scalable, distributed systems in Go (or similar statically typed languages) • Comfort working in cloud-native environments (AWS, GCP) • Familiarity with relational databases (we use MySQL) and an understanding of performance tradeoffs • Experience with observability tooling and operating production systems • A bias for action over perfection, and pride in owning technical decisions Compensation & Benefits We believe in transparency. Starting salary for this role is $150,000 - $200,000 USD (or equivalent in local currency) depending on experience and subject to market rate adjustment. In addition to base salary, this role includes an equity grant in the form of stock options, so you share in the success you help build. We know our people are what make us great, and we’re committed to taking great care of them. Our inclusive benefits package supports your well-being and growth, including 100% coverage of medical, dental, vision, mental health, and supplemental insurance premiums for you and your family . We also offer 16 weeks paid parental leave , unlimited PTO , stipends for remote work and wellness, a professional development budget, and more. See full benefits here → Our Process No gotchas, no trick questions - just a clear, human process designed to help both of us make an informed decision. • Application - We review everyone with care. Tell us why you're interested. • Recruiter Call (30 mins) - Let’s chat about what you’re looking for and how we work. • Hiring Manager Interview (60 mins) - Talk with one of our hiring managers about your working style and a project you've owned end-to-end, plus a short AI-assisted coding exercise. • Technical Interview (60 mins) - A collaborative system design conversation focused on scaling challenges. • Take-Home Assignment - Complet