Watermill is a Go library for building message-driven and event-driven applications. It is not a standalone service; applications embed it and use the core Publisher/Subscriber interfaces to communicate with brokers such as Kafka, RabbitMQ, NATS, Redis Streams, Google Cloud Pub/Sub, AWS SNS/SQS, SQL databases, or an in-memory Go channel. This repository contains the core library, reusable components, runnable examples, and small CLI tools, while broker-specific adapters and some integrations live in separate modules. The architecture is layered. At the bottom are the low-level Pub/Sub abstractions and the Message object with UUID metadata, payload, and Ack/Nack lifecycle semantics. The middle layer is the Router, which wires handlers into consumption loops and supports middleware and publisher/subscriber decorators. On top of that, optional components implement CQRS event/command buses and processors, topic forwarding, request-reply, delayed publishing, metrics, fan-in/fan-out, and requeuing. Middleware covers retry with exponential backoff, poison queues, deduplication, throttling, circuit breaking, correlation IDs, timeout enforcement, and panic recovery. The repository is extensively tested, including a universal pub/sub conformance suite intended for adapter authors to reuse, and GoChannel serves as a complete in-memory reference implementation. The examples demonstrate real production patterns: CQRS with protobuf, ordered events, exactly-once delivery counters, outbox/transactional event forwarding, server-sent event feeds, webhook ingestion, and consumer groups. There is no data research component; this is purely a software library/application framework.
Reacher is an open-source email verification system written in Rust. It checks if an email address exists without sending any email by performing syntax validation, MX record lookup, SMTP connection with intelligent response parsing, and miscellaneous checks (disposable, role-based, gravatar, haveibeenpwned). The system is structured as a Rust workspace with four crates: a core library (`check-if-email-exists`), a CLI binary, an HTTP backend server (`reacher_backend`), and an AWS SQS Lambda worker. The backend provides REST API endpoints for single and bulk email verification, supports queue-based scaling via RabbitMQ, and stores results in PostgreSQL. It features a flexible verification method configuration allowing per-provider overrides (Gmail, Hotmail, Yahoo, etc.) with SMTP, headless browser, or API methods, and supports SOCKS5 proxies with routing rules. The codebase demonstrates strong Rust craftsmanship with clean abstractions, builder patterns, comprehensive error handling, and thorough testing.
This repository is a pure PHP implementation of the AMQP 0-9-1 protocol for interacting with RabbitMQ message brokers. It provides a robust client library handling connection management, channel multiplexing, message publishing/consuming, and wire-level protocol frame encoding/decoding. The architecture features layered abstractions: connection layer (TCP/socket handling), channel layer (logical channels over connections), message layer (AMQP message structure), and wire layer (binary serialization/deserialization). Key entry points include AMQPStreamConnection (primary connection interface) and AMQPChannel (queue/exchange operations). Data flows involve: publishing (user → channel.basic_publish() → AMQPWriter → socket → broker) and consuming (broker → socket → AMQPReader → channel.basic_consume() → user callback). The library supports advanced features like publisher confirms, consumer cancellation notifications, heartbeat monitoring, and batch publishing. The codebase demonstrates strong engineering practices: clear separation of concerns, extensive unit/functional test suite, protocol version handling via generated code from JSON specifications, and active maintenance with recent commits. While supporting broad PHP versions (5.6-8.5), it has dropped older versions showing proactive maintenance. Dependencies are minimal (sockets extension required, pcntl optional for signals). The library is production-ready for building distributed systems requiring reliable asynchronous messaging.
Outpost is a production-grade, multi-tenant event delivery platform by Hookdeck. It ingests events via an HTTP API or message queue adapters (RabbitMQ, AWS SQS, GCP PubSub, Azure Service Bus), routes them to configurable destinations (webhooks, AWS S3/SQS/Kinesis, Azure Service Bus, GCP PubSub, Kafka, RabbitMQ, Hookdeck), and provides end-to-end observability including delivery logs, metrics, alerting, and a self-service user portal. The system is implemented as a modular Go monolith with pluggable storage drivers (PostgreSQL, ClickHouse, Redis) and a clean provider pattern for destination types. It includes generated SDKs for Go, Python, and TypeScript (via Speakeasy), plus a React-based embedded portal. The codebase demonstrates strong engineering practices: abstract backends with conformance test suites, cursor-based pagination, configurable backoff strategies, distributed locking, and comprehensive integration tests covering all destination types. Notable reusable components include a generic LRU cache with TTL, a JSON filter matcher, a cursor pagination library, and an ID generation utility.
This is a comprehensive e-commerce backend platform built with Spring Boot 3.5+, JDK 17, and a multi-module Maven architecture. In production, it serves two distinct APIs: `mall-admin` (admin management) and `mall-portal` (customer-facing storefront), plus a dedicated `mall-search` module for Elasticsearch-powered product search. The system handles product cataloging, order lifecycle management, user registration/authentication, coupon and promotion calculations, shopping cart operations, payment integration (Alipay), and content management (home page banners, recommendations). It uses MySQL as the primary database via MyBatis (with generated mappers), Redis for caching and session management, MongoDB for user activity data (browsing history, favorites), RabbitMQ for delayed order cancellation, and MinIO/Aliyun OSS for file storage. Security is implemented with Spring Security and JWT, including dynamic path-based authorization. The codebase follows a layered architecture (Controller → Service → Mapper/DAO) with shared modules `mall-common` and `mall-security` providing reusable utilities for API responses, pagination, exception handling, Redis caching, and authentication. While heavily reliant on MyBatis Generator for data access objects and includes some long service methods, the overall structure is well-organized and modular, making it suitable as a reference for similar e-commerce projects. No data research or analytical components are present; this is purely an application codebase.
Evolution API is a production-grade, multi-tenant WhatsApp API gateway built with Node.js, TypeScript, and Express. It manages independent WhatsApp instances via Baileys (WhatsApp Web), Meta Business API, and its own Evolution API channel, providing REST endpoints for messaging, chat management, groups, labels, and media. The system integrates deeply with chatbot platforms (Typebot, OpenAI, Dify, Flowise, N8N, EvoAI, EvolutionBot) and event systems (Webhook, WebSocket, RabbitMQ, SQS, NATS, Kafka, Pusher), and includes storage via S3/MinIO and CRM sync with Chatwoot. The architecture follows a modular controller-service pattern with Prisma ORM (supporting MySQL and PostgreSQL), Redis caching, and centralized configuration. It is actively maintained with frequent updates, extensive migrations, and CI/CD pipelines.
Diffgram is a full-stack data annotation platform designed for creating, managing, and reviewing annotations on images, video, audio, text, 3D point clouds, and geospatial data. The system is composed of multiple microservices: a Flask-based REST API (`default`), a background processing service (`walrus`) for media ingestion, export generation, and project migration, an event-driven action runner service (`eventhandlers`) that executes automated workflows (e.g., ML model inference, webhooks, exports), and a Vue 2 + Vuetify single-page application frontend. The backend uses PostgreSQL with SQLAlchemy ORM, RabbitMQ for async messaging, and supports multiple cloud storage backends (AWS S3, GCP, Azure, MinIO). Authentication supports OAuth2/Keycloak, API keys, and session cookies with fine-grained role-based permissions. The platform's core domain includes label schemas, attribute groups, instance templates, task/job management with review workflows, discussions/issues, and a custom query engine for filtering files by labels and attributes. It integrates with external AI services (HuggingFace, Vertex AI, Azure Text Analytics) and labeling vendors (Labelbox, Scale AI). The frontend provides rich annotation tools including 2D canvas (boxes, polygons, keypoints), 3D point cloud annotation with Three.js, audio waveform annotation, text token annotation, and geospatial tile annotation. A command pattern enables undo/redo for annotation actions. The codebase demonstrates solid engineering practices with clear separation of concerns, reusable patterns (strategy, observer, command, policy enforcer), and extensive test coverage (Cypress E2E, Jest unit tests, Python unittest). However, there are signs of technical drift: some outdated dependencies, mixed JavaScript/TypeScript in the frontend, and a few legacy modules marked as deprecated. The open-core model is evident from `OPENCORE - ADD` markers, suggesting proprietary extensions. Overall, Diffgram is a mature, actively maintained annotation platform suitable for teams building training data pipelines.
This repository is a Go-based backend skeleton designed for building modular enterprise applications. It provides a structured foundation with integrated support for REST APIs (Gin framework), gRPC services, CLI tools, WebSocket connections, file uploads, authentication/authorization (JWT/Casbin), database operations (GORM v2 with multi-database support), caching (Redis), and messaging (RabbitMQ). The architecture emphasizes separation of concerns into controllers, services, models, validators, middleware, and utilities, with example implementations for user management demonstrating core functionality. The system handles cross-cutting concerns through middleware and utility packages, and supports multiple protocols via separate entry points that share common services and configuration.
This is a large, scaffolded e-commerce backend system built with the go-zero microservice framework. It implements a full suite of admin and frontend APIs for managing products, orders, members, coupons, content, and system settings. The architecture is microservices-based with separate RPC services for each domain (sys, cms, oms, pms, sms, ums) plus search, consumer, and job services. The codebase is heavily generated using goctl and gorm.io/gen, resulting in a high volume of boilerplate CRUD logic files—many of which are still stubs containing only 'todo: add your logic here' comments. While the system demonstrates a consistent pattern for service decomposition and provides reusable utility packages (pkg/errorx, pkg/time_util, pkg/mq), the majority of business logic is incomplete, and there are signs of technical drift such as duplicate JWT library usage, mixed ORM approaches, and hardcoded configuration values. The project is actively maintained but still in a work-in-progress state, with the README warning of significant backend changes and incomplete frontend adaptation.
This repository is a curated collection of Java interview questions and answers, organized by topics such as Core Java, Collections, Concurrency, Spring, Hibernate, SQL, and more. It also includes several small, self-contained Java projects that demonstrate specific concepts: a custom Stream API implementation (custom-stream), a deadlock example (deadlock), a set of LeetCode algorithm solutions (leetcode-221-maximal-square), and a flawed code review snippet (review). The primary value is the extensive markdown documentation with links to external resources, making it a useful study aid for Java interview preparation. The code examples are educational but not production-grade; the custom-stream project is the most notable for illustrating the internal pipeline pattern of Java Streams. The repository is static and has not been actively updated in some time, though the content remains relevant for many core Java topics.
This repository contains the original open-source codebase for reddit, the social news aggregation and discussion platform. It is a monolithic web application built on the Pylons framework (Python 2), serving both a server-rendered frontend (Mako templates, jQuery, Backbone) and a REST-like API. The architecture relies on multiple data stores: PostgreSQL for core entities (things), Cassandra for high-write data (votes, comments trees, view counts), Memcached/McRouter for caching, and RabbitMQ for asynchronous job processing. It includes a full advertising system, user awards/gold, moderation tools, a wiki, and traffic analytics. While the codebase is archived and relies on heavily outdated dependencies (Python 2, Pylons, pycassa), it showcases several well-designed internal patterns such as a pluggable provider system, a layered cache chain with stale-while-revalidate, and a feature flag framework for A/B testing. These components demonstrate non-trivial engineering skill and could be extracted for reuse. However, the vast majority of the codebase is tightly coupled to reddit-specific models and global state, limiting reusability without significant adaptation.