Misskey

Misskey is a federated, open‑source social‑networking platform built for developers who need a flexible, self‑hosted solution. At its core it implements the ActivityPub protocol to interoperate with other Mastodon‑compatible services, while providing a rich API surface that lets you build custom clients, bots, and integrations. The application is written entirely in TypeScript/Node.js on the backend, with a modern React‑based frontend that communicates via GraphQL and REST endpoints. Data is persisted in PostgreSQL, with Redis used for caching, job queues, and rate‑limiting.

Technical Stack & Architecture

• Backend: Node.js (v18+) + TypeScript, Express‑style router with custom middleware. The codebase is modularized into “services” (e.g., UserService, NoteService) that expose both internal APIs and external GraphQL resolvers.
• Frontend: React + Vite, leveraging TypeScript for type safety. The UI is built as a single‑page application that consumes the GraphQL API and WebSocket events for real‑time updates.
• Database: PostgreSQL is the primary datastore, with a well‑structured schema that supports sharding via logical replication for large deployments. Redis is used as an in‑memory cache and task queue (BullMQ).
• Federation: ActivityPub is fully implemented; Misskey can act as both a client and server, handling inbox/outbox logic, signature verification, and object serialization.
• Containerization: Official Docker images are available on Docker Hub. The repository includes a docker-compose.yml that spins up all required services (API, worker, Redis, PostgreSQL) in a single command.

Core Capabilities & APIs

• GraphQL: A comprehensive schema that exposes user profiles, notes, reactions, notifications, and federation streams. Supports subscriptions for live updates.
• REST: Legacy endpoints for backward compatibility, including OAuth2 support for third‑party clients.
• Webhooks: Publishers can subscribe to events (e.g., new note, user follow) via HTTP callbacks.
• Plugin System: Developers can write plugins in TypeScript that hook into lifecycle events (e.g., onNoteCreated) and expose new routes or modify federation behavior.
• CLI Tools: Administrative commands for database migrations, cache clearing, and instance statistics.

Deployment & Infrastructure

Misskey is designed to run in a containerized environment but can also be installed on bare metal. The Docker image exposes ports for HTTP (80/443) and a separate worker port for background jobs. For scaling, the architecture supports:

• Horizontal Scaling: Multiple API instances behind a load balancer; PostgreSQL can be replicated, and Redis supports clustering.
• Background Workers: Separate containers or pods handle long‑running tasks such as reblog propagation, email notifications, and cache invalidation.
• Observability: Integrated Sentry for error tracking, Prometheus metrics, and Grafana dashboards are available out of the box.

Integration & Extensibility

• OAuth2: Full support for third‑party authentication providers (GitHub, Google) and custom OAuth clients.
• Federation Customization: Hooks to modify outgoing ActivityPub objects, block certain actors, or implement custom moderation policies.
• Event Bus: An internal pub/sub system allows plugins to listen for and react to federation events without touching core code.
• Internationalization: Localization files are maintained in Crowdin, enabling developers to add new languages easily.

Developer Experience

• Documentation: The project hosts extensive docs covering API reference, deployment guides, and plugin development. The docs folder contains Markdown files that are automatically rendered on the website.
• Community: Active Discord and GitHub discussions provide quick support. The codebase follows standard TypeScript conventions, making onboarding straightforward.
• Testing: Codecov and Chromatic integration ensure high test coverage and visual regression testing, which is valuable for plugin authors.

Use Cases

• Self‑Hosted Social Networks: Organizations can run a private, federated community with full control over data.
• Custom Client Development: Build lightweight mobile or desktop clients that consume the GraphQL API and subscribe to real‑time updates.
• Bot Ecosystem: Deploy automated services (e.g., content moderation bots, scheduled posts) as background workers or plugins.
• Federated Chat: Use Misskey’s note system as a foundation for real‑time chat applications with federation support.

Advantages Over Alternatives

Developers choose Misskey when they need a modern, type‑safe stack with robust federation and an extensible plugin system—all while staying within the open‑source ecosystem.