This repository implements `step-ca`, a production-grade online Certificate Authority (CA) server written in Go. It issues X.509 and SSH certificates via multiple protocols including ACME (RFC 8555), SCEP, and JWT-based provisioners. The architecture separates authorization (via pluggable provisioners: JWK, OIDC, AWS, Azure, GCP, Kubernetes, Nebula, X5C, and more) from certificate signing (via CAS backends: softcas, stepcas, cloudcas, vaultcas). The server exposes REST APIs for certificate lifecycle (sign, renew, revoke), SSH certificate management, CRLs, and an admin API for managing provisioners, policies, and webhooks. It supports external key management (AWS KMS, Azure Key Vault, GCP Cloud KMS, HashiCorp Vault) and can run in RA (Registration Authority) mode proxying to an upstream step-ca. The codebase is extensively tested with unit and integration tests, uses a functional options pattern for configuration, and includes a client library for bootstrapping TLS connections. Notable reusable components include a custom error type with HTTP status codes, a policy engine for name constraints, webhook integration framework, request ID middleware, and template rendering engine.