OpenFaaS

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.