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.

Over 8,000 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.

You think like a user, not just an engineer.  You care how your systems power real customer value - and how to make them better.

You bring rigor and creativity. Best practices matter - but never more than forward motion.

• →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
• →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

• 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

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.
• Behavioral Interview (60 mins) - Talk with one of our hiring managers about your experience, values, and working style. We’ll explore topics like ownership, product thinking, and collaboration.
• Technical Interview (60 mins) - A collaborative system design conversation focused on scaling challenges.
• Take-Home Assignment - Complete a short, realistic task similar to what you’d work on here.
• Assignment Review Call (60 mins) - Walk us through your work and discuss tradeoffs, priorities, and how you’d iterate.

All final candidates will be asked to complete a background check and employment verifications as part of our pre-employment process.

Customer.io recognizes the stifling impact of systemic injustice on diverse communities. We commit to using our influence to increase inclusion and equity within the tech industry. We strive to build an inclusive team culture, implement bias-free hiring practices, and develop community partnerships to expand our global impact.

Zoom is the only video conference platform that we use, virtual interviews will be conducted using the video capability (i.e., not via the chat), and offers will be extended in writing on official Customer.io letterhead. Please be vigilant in all of your job search activity, and if you have any questions please contact jobs@customer.io.

We believe in empathy, transparency, responsibility, and, yes, a little awkwardness. If you’re excited by what you read and want to build software that makes communication better for everyone—apply now.