Sr. Software Development Engineer, Annapurna Labs

AWS Networking builds the infrastructure that powers every customer workload in the cloud. ENA Express is a next-generation EC2 networking feature that leverages the Scalable Reliable Datagram (SRD) protocol — developed by AWS — to deliver industry-leading networking performance: dramatically lower tail latency, higher bandwidth utilization, and consistent packet delivery at scale. We are looking for a Senior Software Development Engineer to join the ENA Express team. You will design, build, and own features across the full ENA Express software stack: Firmware on the Nitro-Card, user-space libraries, control plane components, and the performance analytics systems that help our customers get the most out of their network. This is high-ownership work — your code runs on a fleet of millions of EC2 instances, supporting customers who demand the absolute best from their network, including HPC clusters, large-scale ML training, financial services, and other latency-critical applications. Key job responsibilities

• Design and develop features across the AWS Networking software stack on Nitro Cards.
• Deep-dive into ENA Express and the underlying SRD protocol and L3/L4 networking to optimize packet delivery, reduce tail latency, and improve bandwidth utilization.
• Collaborate with hardware and firmware partners to define software/hardware interfaces and surface programmable capabilities to the software layer
• Partner with EC2 platform and service teams to integrate ENA Express features into the broader AWS networking ecosystem
• Mentor junior and mid-level engineers, lead design reviews, and champion engineering best practices across the team
• Drive operational excellence: build observability, contribute to on-call health, and lead incident response and post-mortems About the team We are a team of senior engineers with deep expertise in systems software, networking protocols, and EC2 infrastructure. Our work spans the full stack — from the Firmware on the driver Card, and NIC driver layer up through the EC2 control plane — and we collaborate closely with hardware, firmware, and platform partners. We care deeply about technical craft, operational quality, and each other’s growth.