If you want free, instant-play options to test delivery/infrastructure at small scale before committing, the best choices are usually the ones that give you:

• fast setup
• free tier or trial
• API access / integrations
• basic observability
• easy path to scale later

Here are the strongest options, grouped by use case.

1) General delivery / deployment / app hosting

Vercel

Best for: frontend apps, serverless delivery, quick testing
Why it’s good:

• Very fast to start
• Free tier is generous for prototypes
• Great for testing edge/serverless delivery
• Easy CI/CD from GitHub

Netlify

Best for: static sites, JAMstack, simple app delivery
Why it’s good:

• Instant deployment from Git
• Free tier for small projects
• Good preview builds and rollbacks
• Simple to test global delivery behavior

Cloudflare Pages + Workers

Best for: edge delivery, low-latency infrastructure testing
Why it’s good:

• Strong free tier
• Very quick deployment
• Good for testing edge logic and CDN behavior
• Can scale later with minimal changes

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2) Backend / API infrastructure testing

Render

Best for: simple backend services, APIs, background jobs
Why it’s good:

• Easy to deploy services quickly
• Free tier available for testing
• Good for validating service architecture before scaling

Railway

Best for: fast backend prototypes, databases, and services
Why it’s good:

• Very fast “instant-play” setup
• Easy to connect services and databases
• Great for proof-of-concept infra testing
• Free trial/credits model depending on current plan structure

Fly.io

Best for: globally distributed apps and infra experimentation
Why it’s good:

• Great for testing deployment close to users
• Useful for container-based apps
• Good low-cost/free entry point for validating scaling patterns

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3) Data / queue / event testing

Supabase

Best for: Postgres-backed app testing, auth, storage
Why it’s good:

• Free tier
• Very quick to spin up
• Good for testing app workflows with real backend components
• Useful if you want to validate a scalable app stack

Firebase

Best for: mobile/web backend testing, auth, realtime features
Why it’s good:

• Free tier
• Instant setup
• Strong for testing event-driven and realtime behavior
• Easy to integrate and scale later

Upstash

Best for: Redis/Kafka-like serverless data primitives
Why it’s good:

• Free tier
• Useful for queues, caching, rate limiting
• Good for testing scalable patterns without managing infra

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4) Load / scalability testing tools with free tiers

If your goal is specifically to test scalable infrastructure, you’ll also want a free load-testing tool.

k6 Cloud / k6 OSS

Best for: API and system load testing
Why it’s good:

• Open-source CLI is free
• Can simulate realistic traffic
• Great for validating scaling thresholds

JMeter

Best for: classic performance/load testing
Why it’s good:

• Free and widely used
• Powerful for simulating many users
• Better for deeper performance testing than “demo” tools

Locust

Best for: Python-based load testing
Why it’s good:

• Open-source
• Easy to write user behavior scripts
• Useful for testing service scaling behavior

Artillery

Best for: modern API and event load testing
Why it’s good:

• Simple to run
• Good developer experience
• Great for quick scale checks

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5) Container / orchestration testing

Docker + local Compose

Best for: simulating multi-service infrastructure locally
Why it’s good:

• Completely free
• Best first step before cloud deployment
• Great for validating service dependencies and scaling behavior

Kubernetes local dev tools

Examples: kind, minikube, k3d
Best for: testing Kubernetes-style deployments locally
Why it’s good:

• Free
• Lets you test autoscaling, service discovery, and manifests
• Useful before using managed Kubernetes

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Best picks by scenario

If you want the fastest “works immediately” option:

• Vercel
• Netlify
• Cloudflare Pages

If you want backend + database quickly:

• Supabase
• Railway
• Render

If you want edge/global delivery testing:

• Cloudflare Workers
• Fly.io

If you want actual scalability/load validation:

• k6
• Locust
• JMeter
• Artillery

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Recommended starter stack for free scalable testing

A very practical combo is:

• Frontend: Vercel or Netlify
• Backend/API: Render, Railway, or Cloudflare Workers
• Database: Supabase
• Load testing: k6 or Locust
• Local reproduction: Docker Compose

This gives you a quick path to:

1. deploy instantly,
2. test latency and failure modes,
3. simulate traffic,
4. and see how scaling behaves before paying for production infra.

If you want, I can also give you:

• a ranked top 5 based on your exact use case,
• a comparison table with free-tier limits,
• or a suggested architecture for testing 1k/10k/100k users.