Senior Backend Engineer – Communications (USA Only - 100% Remote)

ABOUT US Since 2013, we’ve been building a CRM that gets out of your way and helps your team sell more, faster. Now we’re building AI into every part of it, so Close does the busywork and your team does the selling. No manual data entry, no 10-click workflows. Just communication-first, AI-powered sales software designed to help you succeed and scale. We're bootstrapped and profitable which means we answer to our customers and play by our rules. We're proud of our 120-person, 100% remote team, focused on building Close so that no small, scaling business fails because it can't figure out sales. OUR STACK Our backend tech stack https://stackshare.io/close-crm/close consists primarily of Python Flask web apps with our TaskTiger https://github.com/closeio/tasktiger scheduler handling many of the backend asynchronous task processing chores. Our data stores include MongoDB, PostgreSQL, Elasticsearch, and Redis. The underlying infrastructure runs on AWS using a combination of managed services like EKS, MSK, RDS and ElastiCache and non-managed services running on EC2 instances. We have CI/CD pipelines that build Docker images, run automated tests and deploy to Kubernetes clusters. We also use these images in our local development environment allowing coding locally against all of our services. We have a well-documented public API https://developer.close.com/ that is consumed by our front-end JavaScript app as well as numerous integrations. Our infrastructure is heavily automated using Terraform, Ansible and other AWS tools. We love open sourcing our code and ideas on our GitHub https://github.com/closeio and on The Making of Close https://making.close.com/, our behind-the-scenes Product & Engineering blog. Check out our open source projects like SocketShark https://github.com/closeio/socketshark, TaskTiger https://github.com/closeio/tasktiger, LimitLion https://github.com/closeio/limitlion and ciso8601 https://github.com/closeio/ciso8601. AI is both how we build and what we ship, and that's reshaped what engineering looks like. This is a transformation we’re embracing and find deeply exciting. ABOUT THE ROLE Close moves 7 million minutes of call recordings, millions of sales emails, and a steady volume of SMS through our pipes every month. The Communications team owns that entire surface — and the job got trickier in the last year, because real-time calling is now a real-time AI problem. When a customer tells our AI Agent Chloe https://close.com/chloe to make a call, everything that happens from that moment on — the live call, the conversation itself — belongs to this team. We're looking for someone energized by both sides of the role: the distributed-systems challenges and the AI challenges. One thing to know up front: we do move people between teams as the work shifts. Most engineers here end up on more than one team over their time at Close — this team is where you'll start, but over time you'll likely have the opportunity to work on many different projects. This role is open at multiple levels — Software Engineer, Senior, and Staff. You don't need to pick one when you apply: we'll calibrate together during the process. YOU ARE - A seasoned engineer. Python is our backbone, but perhaps you've worked across Go, Rust, or TypeScript. You pick the right tool for the workload rather than retreating to what you know. - Deeply experienced with email and calendar platforms. IMAP, sync protocols, calendar APIs, and the thousand edge cases of oddly configured enterprise mail servers. This is the experience that makes someone successful on this team fastest. - Fluent in real-time and async distributed systems. WebRTC, WebSockets, queues, streaming. You've debugged a production incident where latency budgets didn't hold. - Opinionated about AI in real-time workflows. You've built or used live transcription, voice agents, or in-the-loop AI features. You have a view on what's ready for production versus what's still a demo. - At home in the gnar…