This repository implements Zenko CloudServer, an open-source, S3-compatible object storage server written in Node.js. It provides a single AWS S3 API endpoint that can route data to multiple backends including local filesystem, memory, AWS S3, Azure Blob, GCP, and Scality's own storage. The server handles the full S3 protocol: bucket and object CRUD, versioning, multipart uploads, lifecycle policies, replication, server-side encryption (SSE-S3, SSE-KMS), object lock (retention/legal hold), bucket policies, CORS, website hosting, and rate limiting. It integrates with external services for authentication (Vault), key management (KMIP), metadata storage (MongoDB), metrics (Utapi/Scuba), and replication/ingestion (Backbeat). The architecture is a multi-process Node.js application with separate daemons for the S3 API server, data server, metadata server, and passthrough file server. Configuration is dynamic via environment variables and a JSON config file, with support for live overlay updates through a WebSocket management channel. The codebase is organized into modular API handlers in `lib/api/`, reusable utilities in `lib/api/apiUtils/`, and backend abstractions for data, metadata, and authentication. Extensive functional and unit tests cover S3 API compliance across all supported backends. Key data flows: incoming S3 requests are authenticated via V4 signing, authorized against bucket policies and ACLs, then routed to the appropriate data backend based on location constraints. Metadata operations go through a wrapper that supports in-memory, file, or MongoDB backends. Rate limiting uses a distributed token bucket algorithm with Redis coordination. Metrics are pushed to Utapi and exposed via Prometheus. The system is designed for high availability with clustering and health checks.