Senior Software Engineer - Email Channel

Hi, I'm Brian, Senior Director of Engineering at Customer.io. We're looking for experienced engineers who want to own the email channel end to end — from the infrastructure that delivers billions of messages reliably, to the product surfaces our customers use to build, send, and analyze their campaigns. You'll work ...

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.

Build and evolve the frontend experiences customers use to create, preview, and analyze email campaigns — template editors, sending configuration, deliverability dashboards
Design and scale the backend systems that power high-volume email sending, including queue management, retry logic, and event processing (bounces, complaints, deferrals)
Own deliverability-adjacent systems: bounce classification, suppression management, IP/domain reputation monitoring, and feedback loop processing
Partner with our deliverability team to translate domain expertise into automated tooling — reputation scoring, warm-up schedules, sending throttles
Instrument and monitor the health of the email channel: inbox placement signals, block detection, ESP feedback, and alerting
Own problems end to end — from architecture and schema design to testing, deployment, and monitoring
Share knowledge and raise the bar through 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)
Experience building product-facing frontend features in React or similar frameworks, with attention to UX quality and polish
Comfort working in cloud-native environments (AWS, GCP)
Familiarity with relational databases (we use MySQL primarily) and an understanding of performance tradeoffs
Familiarity with high-volume email sending concepts: bounce handling, feedback loops, and delivery event processing
Working knowledge of email authentication standards — SPF, DKIM, DMARC — and how they affect deliverability
Comfortable reasoning about sender reputation, IP warm-up, and ISP behavior at scale
Experience with observability tooling and operating production systems
Experience building or consuming APIs that handle high-throughput async workloads
A bias for action over perfection, and pride in owning technical decisions