# Restate — Durable Execution Engine for Distributed Applications

> Restate is an open-source durable execution engine that makes distributed applications reliable without complex infrastructure. It provides persistent function state, reliable RPC, and workflow orchestration with a lightweight runtime written in Rust.

## Install

Save in your project root:

# Restate — Durable Execution Engine for Distributed Applications

## Quick Use
```bash
# Install the Restate server and CLI
brew install restatedev/tap/restate-server restatedev/tap/restate
# Start the server
restate-server
# In another terminal, register your service endpoint
restate deployments register http://localhost:9080
```

## Introduction
Restate is a durable execution engine that sits between your services and handles the hard parts of distributed computing: retries, state management, idempotency, and workflow coordination. You write ordinary functions in TypeScript, Java, Kotlin, Go, Python, or Rust, and Restate ensures they run to completion even through crashes and restarts.

## What Restate Does
- Provides durable execution: functions resume from where they left off after failures
- Manages persistent state per function invocation without an external database
- Handles reliable RPC between services with built-in retries and deduplication
- Supports workflow patterns like sagas, compensation, and human-in-the-loop approvals
- Offers a journal-based execution model that replays on recovery

## Architecture Overview
Restate is a single-binary server written in Rust that acts as a proxy between callers and service handlers. It intercepts function calls and journals each step (state reads, RPC calls, side effects) in a local log. On failure, the runtime replays the journal to restore the function to its pre-crash state without re-executing side effects. Services connect to Restate via HTTP and communicate using a lightweight protocol over request-response.

## Self-Hosting & Configuration
- Install the server binary via Homebrew, Docker, or download from GitHub Releases
- The server runs as a single process with an embedded log store (RocksDB-based)
- Configure via environment variables or a TOML configuration file
- Services register with Restate by pointing to their HTTP endpoint URL
- The admin API on port 9070 manages deployments, state queries, and invocation inspection

## Key Features
- Language-agnostic: SDKs for TypeScript, Java, Kotlin, Go, Python, and Rust
- Journaled execution ensures exactly-once side effects across retries
- Keyed state: per-key persistent state without external databases
- Virtual objects: stateful entities addressed by key, similar to the actor model
- Built-in invocation scheduling with cron-like timers and delayed calls

## Comparison with Similar Tools
- **Temporal** — mature durable workflow platform; Restate is lighter and embeds state in the runtime itself
- **Inngest** — event-driven durable functions; Restate provides lower-level primitives with more protocol control
- **AWS Step Functions** — managed workflow service; Restate is self-hosted and language-native
- **Dapr** — sidecar-based distributed runtime; Restate focuses specifically on durable execution and journaling
- **Azure Durable Functions** — cloud-tied durable execution; Restate is vendor-neutral and self-hostable

## FAQ
**Q: How is Restate different from Temporal?**
A: Restate embeds state and journaling into a lightweight single-binary server, while Temporal requires a cluster with a separate database. Restate aims for simpler operations with a smaller infrastructure footprint.

**Q: Do I need to change my code to use Restate?**
A: You annotate functions with SDK decorators and use the Restate context for state and RPC, but business logic remains ordinary code. No special DSL or workflow language is needed.

**Q: What happens when the Restate server restarts?**
A: In-flight invocations are replayed from the journal. Side effects already executed are skipped, and the function resumes from the last journaled step.

**Q: Can Restate run in production?**
A: Yes. Restate is used in production by multiple companies. The server supports persistent storage and can handle high-throughput workloads.

## Sources
- https://github.com/restatedev/restate
- https://restate.dev

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Source: https://tokrepo.com/en/workflows/asset-26da7b2f
Author: AI Open Source