Pleroma

Pleroma is a lightweight, fully‑fledged social networking engine that implements the ActivityPub protocol and is interoperable with the broader Fediverse ecosystem. At its core, it offers a modular, Elixir‑based backend that exposes a RESTful API and an extensible JSON‑API for developers who need fine‑grained control over user interactions, content delivery, and federation. The application is designed to be self‑hosted on a wide range of environments—from single‑node VPS deployments to Kubernetes clusters—while keeping resource consumption low enough for modest hardware.

Key Features

• Federation‑Ready: Full support for ActivityPub, allowing seamless interaction with Mastodon, Misskey, Pixelfed, and other Fediverse actors.
• Modular Frontends: Multiple UI options (Pleroma FE, Soapbox, Glitch‑lily) can be swapped without touching the core API.
• Extensible via Plugins: A plugin system written in Elixir lets developers add new routes, modify data models, or hook into lifecycle events.
• Webhooks & Callbacks: Out‑of‑the‑box support for outgoing webhooks on events such as new posts, likes, or follows.
• Rich API: OAuth2 authentication, paginated endpoints, and a well‑documented GraphQL fallback for advanced queries.

Technical Stack

• Language: Elixir (Erlang VM) – guarantees low‑latency concurrency and fault tolerance.
• Framework: Phoenix 1.x – provides the HTTP layer, routing, and real‑time channels via WebSockets.
• Database: PostgreSQL (primary), with optional support for MariaDB/MySQL via Ecto adapters.
• Search: Optional integration with Elasticsearch or MeiliSearch for full‑text indexing.
• Cache & Pub/Sub: Redis is used for session storage, rate limiting, and pub/sub messaging between instances.
• Containerization: Official Docker images are maintained; Helm charts exist for Kubernetes deployments.

Deployment & Infrastructure

Pleroma can run on a single VM with as little as 1 GB RAM and 1 core, making it ideal for hobbyist servers. For higher throughput, the application scales horizontally by running multiple Phoenix nodes behind a load balancer; shared state is maintained in Redis and PostgreSQL. The configuration system uses environment variables and a config.exs file, enabling zero‑touch deployments via Docker Compose or CI/CD pipelines. Continuous integration is supported by the project's GitLab instance, which also hosts automated tests and vulnerability scans.

Integration & Extensibility

• Plugin API: Developers can write plugins that register new routes, modify request/response pipelines, or tap into event hooks.
• Webhooks: Subscribers can register callbacks for federation events, enabling third‑party services (e.g., analytics, moderation bots).
• Custom Frontends: Since the backend is API‑centric, any modern framework (React, Vue, Svelte) can consume Pleroma’s endpoints.
• OAuth & OpenID Connect: Integration with external identity providers is straightforward, allowing single‑sign‑on scenarios.

Developer Experience

The documentation is comprehensive and includes a dedicated API reference, migration guides, and plugin tutorials. The community is active on GitLab issues, Discord, and the Fediverse itself, providing rapid feedback loops. Configuration is declarative, with clear defaults that work out of the box, yet advanced users can fine‑tune performance knobs (e.g., worker pools, cache sizes). Licensing under the AGPLv3 ensures that any derivative work remains open source, which appeals to developers who value transparency.

Use Cases

1. Micro‑Community Hosting: Small groups or organizations can deploy a private instance with minimal resources, leveraging Pleroma’s low overhead.
2. Federated Analytics Platforms: By subscribing to webhooks, developers can build dashboards that aggregate cross‑instance metrics.
3. Custom Frontend Projects: Teams building bespoke UIs can consume Pleroma’s API without re‑implementing federation logic.
4. Educational Environments: Instructors can set up a sandboxed instance to teach students about distributed social networks and ActivityPub.

Advantages Over Alternatives

• Performance: Elixir’s lightweight processes allow thousands of concurrent connections with minimal CPU usage.
• Flexibility: The plugin system and API‑first design let developers extend functionality without forking the core.
• Scalability: Horizontal scaling is straightforward thanks to stateless Phoenix workers and Redis pub/sub.
• Licensing: AGPLv3 encourages open collaboration while protecting the core from proprietary forks.
• Community: A vibrant developer community ensures rapid issue resolution and continuous feature enrichment.

In summary, Pleroma offers a technically robust, extensible platform for developers who need a self‑hosted, federation‑ready social network that can be tailored to niche requirements while remaining lightweight and highly scalable.