Staff Software Engineer - Site Defense

About the Role

Reddit's Transport and Site Defense teams build and operate foundational infrastructure behind one of the largest sites in the world. These teams own how requests enter Reddit, how services discover and talk to each other, how traffic moves across clusters and clouds, and how Reddit protects itself from DDoS attacks, scrapers, bots, and other undesired traffic.

We are looking for a Staff Software Engineer to join the Site Defense team within Reddit’s Infrastructure organization. Site Defense is responsible for protecting Reddit at internet scale—serving as the first line of defense against DDoS attacks, automated abuse, large-scale scraping, and other network-level threats. This is a high impact role that sits at the intersection of distributed systems, networking, security, and applied machine learning. You will design and own the critical infrastructure that safeguards Reddit’s data from large scale attacks.

Responsibilities

• Design, build, and operate high-scale, low-latency systems that protect Reddit from DDoS attacks, bots, and automated abuse.
• Analyze, develop and evolve ingress-level defenses across CDN, edge, and internal infrastructure layers.
• Build systems to detect, score, and mitigate malicious traffic in real time at per-request and per-user granularity.
• Partner closely within Infrastructure and with Security, and internal Safety teams to balance security, performance, and user experience.
• Mentor junior engineers in their professional growth.
• Contribute to the team’s ML-at-Ingress initiatives, including experimenting with models for traffic classification, bot detection, and anomaly detection.
• Own services end-to-end, including design, implementation, on-call, and operational excellence.
• Participate in incident response and post-incident analysis for large-scale network or abuse events.

Requirements

• 7+ years of experience building and operating high throughput and low latency production distributed systems.
• Software development experience in one or more general purpose programming languages: Python, Go, Rust, Java, C++.
• Excellent communication skills to collaborate with a service-oriented team and company.
• Experience building and maintaining distributed, fault-tolerant distributed systems at scale.
• Experience with networking fundamentals (HTTP, TLS, TCP/IP, proxies, CDNs, load balancing).

Nice to Have

• Experience with DDoS mitigation, WAFs, bot management, or abuse prevention systems.
• Experience with anti-abuse frameworks and bot scores (ReCaptcha, Datadome, Turnstile).
• Experience with browser fingerprinting frameworks (fingerprintJS, ThumbmarkJS).
• Familiarity with ML systems in production, especially real-time inference or feature pipelines.

Interview Process Notice

In select roles and locations, interviews may be recorded, transcribed, and summarized by artificial intelligence (AI). Candidates will have the opportunity to opt out prior to scheduled interviews.