Iii
Effortlessly compose, extend, and observe every service in real-time for the first time ever.
Last verified:
What is Iii?
iii (pronounced "three eye") is a backend unification and orchestration system that makes it possible to effortlessly compose, extend, and observe every service in real-time. It transforms a backend from behaving like separate services into a single application-level interface across all services by creating one integration point for all backend systems. iii organizes software into three primitives: Worker, Trigger, and Function—something hosts work, something causes it, something does it.
The system unifies any backend stack with a single engine and three primitives. Key features include durable orchestration, interoperable cross-language execution, live discovery of functionality, live system extensibility, and live system observability. Built-in workers provide queues, cron scheduling, HTTP endpoints, pub/sub messaging, key-value state management with reactive triggers, real-time streaming, sandboxing via ephemeral microVMs, OpenTelemetry-based observability, and WebSocket bridging. The iii CLI enables triggering functions, managing workers, launching the web console, and deploying to the cloud.
iii is built for developers building production-grade backends, platform teams publishing capabilities, application teams registering functions, and AI agents. It supports any language and runtime—workers can run in Docker, Kubernetes, on the edge, in browser tabs, on Raspberry Pi, or inside hardware-isolated microVMs. The system is inherently agentic since agents are workers that can act on every part of the system. It enables faster onboarding of new developers and AI agents, simpler debugging across systems, reduced switching costs, and faster delivery of backend features.
Iii pricing
Pricing model: Freemium
iii is free to use with an open-source engine. The CLI installs the engine via curl script, and the engine includes all built-in workers (HTTP, Queue, Cron, PubSub, State, Stream, Sandbox, Observability, Worker Manager) without separate installation. There is a free tier with full functionality for local development and self-hosted production deployments. iii Cloud hosted deployments are announced but not yet available. Users can opt out of anonymous usage data collection via the disable-telemetry option.
Iii pros
- Reduces quadratic coordination cost of service integration to zero
- Three simple primitives (Worker, Trigger, Function) for all capabilities
- Cross-language execution supports Node.js, Python, Rust, and browser SDKs
- Live system extensibility—add workers at runtime with zero downtime
- Live discovery of all functions in the system across all workers
- Built-in workers: queues, cron, HTTP, pub/sub, state, stream, sandbox, observability
- Durable orchestration with automatic retry and dead-letter queue support
- Interactive web console for monitoring, debugging, and testing functions
- Built for AI agents—agents are workers with system-wide access
- One mental model for humans and agents simplifies onboarding
- Deploy anywhere: Docker, Kubernetes, edge, browser, Raspberry Pi, microVMs
- OpenTelemetry integration for distributed traces, metrics, and logs
- Topic-based and named queues with configurable retries and FIFO ordering
- Reactive state management with triggers that fire on state changes
- CLI enables triggering functions, managing workers, and scaffolding projects
- No bespoke SDKs or per-service API contracts between teams
- Ephemeral microVM sandboxing for isolated code execution
- Channel support for bidirectional binary data streaming between functions
Iii cons
- iii Cloud hosted deployments not yet available
- Requires learning new primitives and architectural model
- Engine runs locally on WebSocket (ws://localhost:49134) by default
- In-memory OpenTelemetry config by default requires config.yaml for production
- Relatively new tool with smaller ecosystem than established frameworks
- Migration from Motia required for existing Motia users
- Browser SDK requires explicit connection handling unlike Node.js auto-connect
- Python and Rust SDKs require explicit connect() call
- Development still in active change with version 0.11.0 recent release
Frequently asked questions about Iii
What is iii?
iii is a backend unification and orchestration system that organizes software into three primitives—Worker, Trigger, and Function—to transform backends from separate services into a single application-level interface. It enables effortless composition, extension, and observation of every service in real-time.
What are the three primitives in iii?
The three primitives are Worker (something that hosts work), Trigger (something that causes work to happen), and Function (something that does the work). Every capability including queues, cron, streaming, sandboxing, observability, agents, and business logic can be built from these three things.
How do I install iii?
Install the iii engine by running: curl -fsSL https://install.iii.dev/iii/main/install.sh | sh. Then verify with 'iii --version' and start the engine with 'iii --use-default-config'.
What programming languages does iii support?
iii supports Node.js, Python, Rust, and browser/TypeScript through official SDKs. Workers can be written in any language since the engine handles serialization and routing via WebSocket.
What built-in workers are included?
Built-in workers include: iii-http (HTTP endpoints), iii-queue (async job processing), iii-cron (scheduled tasks), iii-pubsub (topic-based messaging), iii-state (key-value state), iii-stream (real-time subscriptions), iii-sandbox (ephemeral microVMs), iii-observability (OpenTelemetry), and iii-worker-manager (WebSocket bridge).
How does iii handle observability?
iii has built-in OpenTelemetry integration providing distributed traces, runtime metrics, and structured logs. The engine starts with in-memory OpenTelemetry configuration, making traces, metrics, and logs available without creating config.yaml first.
What is the iii Console?
The iii Console is a web-based developer console for monitoring, debugging, and interacting with a running iii engine. You launch it with 'iii console' and use it to test functions, triggers, state, and queues interactively.
How do queues work in iii?
iii supports both topic-based queues (multiple functions subscribe to a topic, message fans out to all subscribers with independent retries) and named queues (jobs enqueued to specific functions with configurable retries, concurrency limits, FIFO ordering, and dead-letter support).
Is iii built for AI agents?
Yes, iii is inherently agentic. Agents are workers that can act on every part of the system, not inside a separate agent runtime. An agent's tools are functions, its memory is state, and its orchestration is triggers. Agents can register new workers at runtime to extend the system.
What is iii Cloud?
iii Cloud is the hosted deployment option for iii that will manage production deployments. The 'iii cloud' CLI subcommand is available to manage hosted deployments, but iii Cloud is not yet available as of the current documentation.