Guardrail Service is a production-grade LLM input validation system built to detect prompt injection and jailbreak attacks before they reach a language model. It uses a two-tier pipeline — a sub-millisecond rule engine powered by Aho-Corasick pattern matching, followed by a quantized DeBERTa transformer exported to ONNX for semantic attack detection at ~20ms. The service runs as an internal HTTP API built with FastAPI, containerized with Docker, and monitored via Prometheus and Grafana. It includes an adversarial test suite of 100+ prompts achieving 95%+ detection accuracy with under 5% false positives, and a live dashboard showing real-time validation, pipeline flowchart, and benchmark results.