Serverless

3 open source tools compared. Sorted by stars — scroll down for our analysis.

Tool	Stars	Velocity	Language	License	Score
OpenFaaS Serverless Functions Made Simple	26.1k	+7/wk	Go	MIT License	79
serverless-step-functions	1.0k	+1/wk	JavaScript	MIT License	67
functions-framework-dart	547	—	Dart	Apache-2.0	64

Our Analysis

OpenFaaS26.1k★

OpenFaaS lets you deploy functions to any Kubernetes or Docker Swarm cluster without locking into AWS Lambda or Google Cloud Functions. Write a function in any language, package it as a container, deploy it, and OpenFaaS handles scaling, routing, and health checks. Go, mixed licensing (Community Edition is MIT, Pro is commercial). The architecture is straightforward: a gateway routes requests to function pods, the autoscaler adjusts replicas based on demand, and Prometheus provides metrics. Supports async invocation via NATS for long-running tasks. Community Edition (CE) is free and covers the core: deploy functions, auto-scale, invoke via HTTP or async. It works. But the Pro tier gates features that matter at scale: scale-to-zero (functions that shut down when idle), single sign-on, detailed dashboard, retry policies, and Kafka event triggers. Pro pricing starts at $295/mo for 1 installation. Enterprise is custom. Solo developers: CE is fine for personal projects. Run it on a $10/mo VPS or your home lab. Small teams: CE works but you'll feel the missing scale-to-zero quickly; idle functions eating resources adds up. Medium to large: Pro is where OpenFaaS becomes production-viable. The catch: the serverless-on-your-own-infra space is niche. If you're already on AWS, Lambda is simpler. If you need Kubernetes functions specifically, Knative is fully open source with scale-to-zero included. OpenFaaS Pro's pricing makes sense only if you're committed to self-hosted serverless and want a polished developer experience.

serverless-step-functions1.0k★

This plugin lets you define AWS Step Functions directly in your serverless.yml. Instead of going to the AWS console and clicking through the Step Functions designer, you write the state machine definition alongside your Lambda code and deploy it all together. The plugin is free and open source. It doesn't have its own license file clearly posted, but it's a community plugin for the Serverless Framework ecosystem. There's nothing to host. It's a Serverless Framework plugin: `npm install` it, add it to your config, and it deploys Step Functions state machines to AWS when you run `serverless deploy`. The ops burden is trivial because AWS manages the actual Step Functions infrastructure. Solo developers: if you're already on Serverless Framework and need Step Functions, this saves you from writing CloudFormation by hand. Small teams: same story: it keeps your workflow definitions in version control next to your functions. Beyond that: at scale, you might prefer CDK or Terraform for more control. The catch: this is tightly coupled to the Serverless Framework. If you move to CDK, SAM, or SST for your infrastructure, this plugin doesn't come with you. Also, development has slowed; the last meaningful updates were a while back. It works, but don't expect rapid feature additions.

functions-framework-dart547★

This is the framework that makes it work. It gives you a local development server and the scaffolding to write HTTP and CloudEvent handlers that deploy directly to Cloud Functions or Cloud Run. Apache 2.0, Google-maintained. It's a thin layer. You write a Dart function, annotate it, and the framework handles the HTTP server, request parsing, and function routing. Works with the Dart package ecosystem via pub.dev. Fully free. No paid tier exists. It's a framework, not a service. You pay Google Cloud for compute when you deploy, but the framework itself costs nothing. Solo Dart developers experimenting with serverless: useful if you're committed to Dart on the backend. Small teams: only makes sense if your whole stack is Dart (Flutter front + Dart backend). Larger teams: almost certainly using Node, Python, or Go for Cloud Functions already. The catch: the Dart serverless ecosystem is tiny, and zero velocity tells you adoption is niche. If your function needs packages that don't exist in Dart, you're stuck. Node.js or Python Cloud Functions have 100x the community support.