Provides `withFileLock` and `atomicWriteFile` functions for safe concurrent file access using file system locking. Idempotent, handles race conditions, and can be extracted as a standalone utility for any Node.js project requiring coordinated writes to shared config files.

Implements a sliding window bucket algorithm for rate tracking (QPS, TPS, RPM). Supports variable window sizes and resolution, increment operations, and peak calculation. Self-contained and reusable for any application needing lightweight rate monitoring without external dependencies.

Abstract base class for protocol converters defining a consistent interface (`convertRequest`, `convertResponse`, `convertStreamChunk`, `convertModelList`). New providers can be added by subclassing and registering with ConverterFactory. Demonstrates clean separation of concerns and is reusable as a template for any API transformation layer.

Manages multiple credentials/accounts per provider type with support for health monitoring, LRU-based selection, concurrency limits (slot queue), automatic token refresh, and accelerated recovery for unhealthy nodes. Persists state with debounced writes to a JSON file. Could be extracted to manage any set of authenticated API credentials with rotation and failover.

Structured logger with support for _AsyncLocalStorage_ request context, multiple log levels, console and file output, log rotation, and configuration from environment variables. Self-contained and easily adaptable to other Node.js services requiring correlation IDs and centralized logging.