Senior Detection Engine Engineer (R&D)

Castle (Headquarters: )

Detection Engineering R&D Security Data Pipelines Real-time Systems Automation Rule Engine Fingerprinting Signal Ingestion AI Infrastructure Backend Remote EMEA Scalability Low Latency Distributed Systems AI Engineer Back End Engineer Data Engineer Staff Engineer

Castle is a YC-backed Series A startup building modern, AI-powered bot detection and abuse prevention technology used by companies like Canva, Atlassian, and Rockstar Games. Our platform processes billions of requests monthly with low latency (~100ms), focusing on real-time protection and behavioral intelligence to fight fraud and abuse. We are a small, fast-moving team committed to staying ahead of attackers.

As a Senior Detection Engine Engineer in our R&D team, you will be responsible for building and scaling the core infrastructure that powers our detection logic. This is a deeply technical role focused on the high-performance systems at the heart of Castle's product.

Responsibilities:
- Design, develop, and scale critical backend systems including our rules engine, device fingerprinting pipelines, and high-speed signal ingestion infrastructure.
- Integrate AI-driven detection models and insights into the core engine.
- Develop and implement auto-adaptive logic that allows our systems to react to emerging threats in real time.
- Focus on building highly reliable, scalable, and low-latency real-time systems capable of handling significant load.
- Implement automation for system management, deployment, and monitoring.
- Collaborate closely with ML engineers and security researchers to operationalize new detection strategies and models.
- Contribute to the core architecture of our detection stack, ensuring it effectively stops various abuse vectors like fake accounts, account takeovers (ATO), multi-accounting, content abuse, SMS pumping, and transaction fraud.

Ideal Candidate:
- Strong background and significant experience in backend engineering, particularly with a focus on security, data pipelines, or real-time analytics systems.
- Proven ability to design, build, and operate high-throughput, low-latency distributed systems.
- Experience with technologies relevant to rule engines, data streaming/processing (e.g., Kafka, Flink), device fingerprinting techniques, or high-speed data ingestion.
- Enjoys tackling complex technical challenges in the domains of real-time systems, security, and large-scale data processing.
- Experience with integrating ML models into production systems is a plus.
- Passionate about building robust infrastructure and automation to outsmart fraudsters.
- Comfortable working in a fast-paced R&D environment and taking ownership of critical systems.