Senior Machine Learning Engineer, ML Efficiency

Reddit has a flexible workforce! If you happen to live close to one of our physical office locations our doors are open for you to come into the office as often as you'd like. Don't live near one of our offices? No worries: You can apply to work remotely in any country in which we have a physical presence.

About the Role

Reddit is building a dedicated Ads ML Efficiency function to make model training and inference materially faster, cheaper, safer, and more scalable. This person will be a key senior engineer on that team, owning meaningful efficiency work across training systems, inference and serving paths, launch-readiness tooling, and reusable optimization capabilities for Ads ML.

This role sits at the intersection of ML modeling, systems optimization, and engineering leverage. The engineer will partner closely with ranking teams, serving owners, and ML Platform to identify important bottlenecks, land measurable efficiency wins, and help build the mechanisms that make those wins repeatable.

What you’ll do

• Independently own high-value optimization initiatives across training, inference, or launch-readiness for important Ads ML workloads.
• Diagnose bottlenecks in real production systems using profiling, benchmarking, and observability rather than intuition-first debugging.
• Build performance tooling, optimization playbooks, observability hooks, guardrails, or efficiency primitives that help more than one team or workload over time.
• Improve launch-safety and efficiency readiness by contributing to load testing, fallback readiness, latency and cost visibility, and operational confidence for heavy models.
• Work with model owners and platform teams to land pragmatic fixes while helping the team gradually standardize repeated solutions.
• Contribute to the team’s technical direction by surfacing patterns, tradeoffs, and opportunities for reuse or automation.
• Mentor less-experienced engineers through code, debugging, measurement rigor, and strong execution habits.

What we’re looking for

• Deep ML systems experience close to real production models and workloads, not just generic infra exposure.
• Direct hands-on experience improving training or serving efficiency with measurable outcomes.
• Strong technical judgment across model-level, runtime-level, and infrastructure-level optimization choices.
• Ability to own complex projects end to end and collaborate effectively across team boundaries.
• Good customer and platform instincts: can solve concrete bottlenecks while keeping maintainability, adoption, and future reuse in mind.
• Strong communication: able to explain tradeoffs clearly to engineers and partner teams.

Nice-to-have

• Experience with GPU training or serving migrations.
• Experience with PyTorch,