Arroyo

Free plan Open source APILinuxMacSelf-hostedWeb

What Arroyo is

Arroyo is an open-source stream processing engine for running stateful computations on data streams and returning results in under a second. Teams define pipelines in analytical SQL, including queries with windows and joins, and can extend SQL with Rust scalar, aggregate, and asynchronous functions. Arroyo supports exactly-once processing and state checkpointing for recovery. Its connectors cover systems such as Kafka, Kinesis, MQTT, MySQL, Postgres, Redis, Delta Lake, and Iceberg, alongside HTTP, WebSocket, and webhooks. It reads and writes JSON, Avro, Parquet, text, and binary, and includes more than 300 SQL functions. Arroyo says it can handle millions of events per second and supports horizontal and vertical rescaling. The web UI supports connection management, query development and testing, and pipeline monitoring; a REST API can also manage pipelines. A single-node cluster is intended for development and testing, while production deployments use a distributed cluster with Arroyo’s scheduler or Kubernetes. It is free, Apache 2.0 licensed, and self-hostable.

Who it suits

Arroyo suits teams building stateful streaming pipelines with SQL, including those that need Rust extensions or a choice of self-hosted production deployment. Its single-node cluster is intended for testing and development.

What it does well

Free, open-source, Apache 2.0 licensed engine
SQL supports complex queries, windows, and joins
Over 300 SQL functions and Rust extensions
Checkpointing and exactly-once processing
Web UI and REST API for pipeline management

What to know first

Production deployments require a distributed cluster
Single-node cluster is for testing and development

Limits

The single-node cluster is intended for testing and development; production deployments use a distributed cluster with Arroyo’s scheduler or Kubernetes. The listed plan is free and Apache 2.0 licensed.

Plans

Plan	Billed and limits	Price
Open-source Arroyo Engine	Apache 2.0 licensed; single binary; self-hosted	Free
Arroyo open-source	Apache 2.0 engine · self-hosted on Linux/macOS, Docker or Kubernetes	Free
Cloudflare Workers Paid with Pipelines	monthly · 50 GB/month SQL transforms · 50 GB/month sink delivery · unlimited stream ingress · $0.04/GB additional SQL · $0.03/GB JSON sink · $0.06/GB Parquet/Iceberg sink	$5 a month

As arroyo.dev lists them, read 4 Oct 2026. The maker's own page has the final word.

Getting started

Open the Arroyo website.
Use the free Apache 2.0 licensed engine, available as a single binary for self-hosting.
Run a single-node cluster for testing and development.
For production, deploy a distributed cluster using Arroyo’s built-in scheduler or Kubernetes.
Manage connections, develop and test SQL queries, and monitor pipelines in the web UI, or manage pipelines through the REST API.
Configure checkpoint and artifact storage using a supported option such as an S3-compatible store, R2, GCS, Azure Blob Storage, or a local filesystem.

Verdict

Arroyo combines SQL-based streaming, recovery features, and a broad connector list in a self-hostable engine. Plan for a distributed cluster for production use.

Questions

How much does Arroyo cost?

The Open-source Arroyo Engine plan is free. It is Apache 2.0 licensed, available as a single binary, and self-hosted.

Is Arroyo open source?

Yes. The engine is Apache 2.0 licensed and self-hostable. Arroyo said it would remain open-source and self-hostable after its announced acquisition by Cloudflare in April 2025.

Which platforms are listed?

Arroyo is listed for API, Linux, macOS, self-hosted, and web.

What languages can I use for pipelines?

Users define pipelines with analytical SQL. Rust scalar, aggregate, and asynchronous user-defined functions can extend SQL.

What deployment options are available?

A single-node cluster is intended for testing and development. Production deployments use a distributed cluster with Arroyo’s built-in scheduler or Kubernetes.

Which storage systems can hold checkpoints and artifacts?

Options include S3-compatible stores, R2, GCS, Azure Blob Storage, and local filesystems.

Facts from Arroyo's own pages

Acquisition: Cloudflare announced on April 10, 2025 that it acquired Arroyo and would integrate its engine into Cloudflare Pipelines, Queues, Workers and R2. · blog.cloudflare.com, 15 Oct 2026
Async UDF limits: Async Rust UDFs have configurable concurrency and timeout settings; Python UDFs do not support async functions. · doc.arroyo.dev, 15 Oct 2026
Checkpoint storage: Production deployments can store checkpoints in S3, Google Cloud Storage, Azure Blob Storage or compatible stores such as Minio, R2 and Backblaze B2. · doc.arroyo.dev, 15 Oct 2026
Cloudflare managed limits: Cloudflare's current Pipelines pricing page lists unlimited stream ingress, 50 GB/month included SQL transforms and 50 GB/month included sink delivery on Workers Paid. · developers.cloudflare.com, 15 Oct 2026
Company history: Arroyo’s founders say they started the company in 2022 and open-sourced the engine in 2023. · arroyo.dev, 4 Oct 2026
Company legal name: Crunchbase identifies the company legal name as Arroyo Systems, Inc. · crunchbase.com, 15 Oct 2026
Company location and investors: Crunchbase lists Berkeley, California as headquarters and Y Combinator as the investor in its pre-seed round. · crunchbase.com, 15 Oct 2026
Connectors: Documented connectors include Kafka, Confluent Cloud, Kinesis, MySQL, Postgres, MQTT, NATS, Redis, Redpanda, Fluvio, Filesystem, Iceberg, WebSocket, SSE, Webhook and HTTP polling. · doc.arroyo.dev, 15 Oct 2026
Data formats: Native formats include JSON, Avro, Parquet, raw text and raw binary, with custom formats possible through UDFs. · arroyo.dev, 15 Oct 2026
Deployment: Arroyo can run as a single binary, Docker container or Kubernetes deployment, with SQLite for local use and Postgres recommended for distributed production. · doc.arroyo.dev, 15 Oct 2026
Exactly-once processing: Arroyo advertises exactly-once processing across out-of-order data and machine failures, using checkpointed state. · arroyo.dev, 15 Oct 2026
Fault tolerance: The engine supports state checkpointing for fault tolerance and pipeline recovery, and exactly-once processing. · doc.arroyo.dev, 4 Oct 2026
Formats and functions: Arroyo natively reads and writes JSON, Avro, Parquet, text, and binary, and includes over 300 SQL functions. · arroyo.dev, 4 Oct 2026
Founded: 2022 · arroyo.dev, 28 Sept 2026
Founder and launch: Y Combinator lists Arroyo as a Winter 2023 company founded in 2022 with founders Micah Wylde and Jackson Newhouse. · ycombinator.com, 15 Oct 2026
GitHub project: The public repository describes Arroyo as a Rust distributed stream-processing engine and showed about 5.1k stars and 379 forks when opened. · github.com, 15 Oct 2026
Helm packaging: Artifact Hub lists an official Arroyo Helm chart for Kubernetes and showed chart/application version 0.15.0. · artifacthub.io, 15 Oct 2026
Joins: Arroyo SQL supports stream joins including inner, left, right and full joins, plus windowed and updating-data joins. · arroyo.dev, 15 Oct 2026
Kafka integration: Kafka sources and sinks support self-hosted Kafka, Amazon MSK and Confluent Cloud, with exactly-once or at-least-once sink modes. · doc.arroyo.dev, 15 Oct 2026
Licence: The official documentation states that Arroyo is fully open source under the Apache 2.0 licence. · doc.arroyo.dev, 15 Oct 2026
Limit: late events: Events arriving after a watermark has passed are dropped according to the documented watermark semantics. · doc.arroyo.dev, 15 Oct 2026
Limit: operational burden: The same independent review says self-hosted deployments leave infrastructure responsibility with the customer team. · cloudimg.co.uk, 15 Oct 2026
Limit: state memory: The concepts documentation says open-source Arroyo stores operator state in worker memory, limiting state size to available worker memory. · doc.arroyo.dev, 15 Oct 2026
Postgres integration: Postgres connectivity currently uses Debezium through Kafka; the documentation says a native Postgres connector is planned. · doc.arroyo.dev, 15 Oct 2026

Where Arroyo stands on Freedom251

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