# What are you building? The 21 use cases of The Stack

> Nicolas Dao's picks (Cloudless Labs, Sydney) for each job, in order of preference. Each link is that job's full file: the picks with notes, what to avoid and what to use instead.

- Web page: https://cloudlesslabs.com/stack/use-cases/

- [An API for my app](https://cloudlesslabs.com/stack/use-cases/api/index.md): I need a backend API that reads and writes a database. Picks: Lambda function URLs, Neon (serverless Postgres), Lambda Web Functions, Cloudflare Workers.
- [An AI chat or LLM feature](https://cloudlesslabs.com/stack/use-cases/ai-chat/index.md): My app needs to call an LLM and stream the answer to users. Picks: Cloudflare Workers, OpenRouter, pgvector, Cloudflare AI Gateway.
- [Something live that many people watch at once](https://cloudlesslabs.com/stack/use-cases/realtime/index.md): Live auctions, collaborative editing, polls, chat rooms, game lobbies. Picks: Cloudflare Workers, Cloudflare Durable Objects, Neon (serverless Postgres), Amazon S3.
- [A traffic spike I can see coming](https://cloudlesslabs.com/stack/use-cases/flash-sale/index.md): A flash sale, ticket drop or launch where thousands hit at once. Picks: Cloudflare Workers, Cloudflare Durable Objects, AWS Lambda, Stripe.
- [A website, SPA or PWA](https://cloudlesslabs.com/stack/use-cases/website/index.md): A marketing site or a front-end app. Picks: Cloudflare static hosting, Cloudflare R2, Astro on Cloudflare Workers, Next.js on Cloudflare Workers (OpenNext), Cloudflare Turnstile.
- [Background jobs and retries](https://cloudlesslabs.com/stack/use-cases/background/index.md): Work that runs after the request, with retries. Picks: Amazon SQS, AWS Lambda, Amazon EventBridge, Lambda durable functions.
- [Event-driven plumbing](https://cloudlesslabs.com/stack/use-cases/events/index.md): Moving events between services, buffering work, fanning out and streaming records into the lake. Picks: Amazon EventBridge, Amazon SQS, Amazon SNS, Amazon Data Firehose, Amazon Kinesis.
- [A job that runs for hours](https://cloudlesslabs.com/stack/use-cases/long-job/index.md): A nightly import, report or migration longer than 15 minutes. Picks: Fargate scheduled tasks, Amazon EventBridge.
- [Device and IoT data](https://cloudlesslabs.com/stack/use-cases/iot/index.md): Thousands of devices sending readings that end up in reports. Picks: AWS IoT Core, Amazon SQS, Neon (serverless Postgres).
- [Semantic search and RAG](https://cloudlesslabs.com/stack/use-cases/search/index.md): Search by meaning, or feed an LLM your documents. Picks: pgvector, Amazon S3 Vectors.
- [Sending email](https://cloudlesslabs.com/stack/use-cases/email/index.md): Transactional emails and newsletters. Picks: Resend, Amazon SES.
- [A database](https://cloudlesslabs.com/stack/use-cases/database/index.md): Where the data lives. Picks: Neon (serverless Postgres), Aurora PostgreSQL.
- [A data lake](https://cloudlesslabs.com/stack/use-cases/data-lake/index.md): Analytics over everything the apps produce, cheaply, without a warehouse to run. Picks: Amazon S3, Amazon Data Firehose, S3 + Glue + Athena, DuckDB, Aurora PostgreSQL.
- [Provisioning everything](https://cloudlesslabs.com/stack/use-cases/infra/index.md): Infrastructure as code across AWS and every vendor. Picks: Pulumi.
- [Private access and exposing a box](https://cloudlesslabs.com/stack/use-cases/private-access/index.md): Reach private AWS resources, or publish a service from a server. Picks: Tailscale, Cloudflare Tunnel (cloudflared).
- [Logs without a shocking bill](https://cloudlesslabs.com/stack/use-cases/logging/index.md): Observability that doesn't cost more than the app. Picks: Amazon CloudWatch, Amazon Data Firehose, DuckDB, Cloudflare Workers.
- [An AWS foundation for a client](https://cloudlesslabs.com/stack/use-cases/aws-foundation/index.md): Accounts, access, backups and cost from day one. Picks: AWS Organizations + IAM Identity Center, Pulumi, AWS Backup, Savings Plans and Reserved Instances, Cost Explorer (with Claude Code).
- [Moving on-premises systems to AWS](https://cloudlesslabs.com/stack/use-cases/migration/index.md): Lift databases and apps into AWS. Picks: Claude Code, AWS Database Migration Service, AWS Organizations + IAM Identity Center, Pulumi.
- [Building with AI agents](https://cloudlesslabs.com/stack/use-cases/ai-dev/index.md): How I write and test code now. Picks: Claude Code, OpenAI Codex, Playwright, Vitest, pytest, Stryker mutation testing, GitHub, Self-hosted MCP servers.
- [Sign-in and identity](https://cloudlesslabs.com/stack/use-cases/sign-in/index.md): How users sign in, reset passwords and use Google, Microsoft or their company login. Picks: Better Auth, Amazon Cognito, Resend, Cloudflare Workers.
- [Running the business](https://cloudlesslabs.com/stack/use-cases/business/index.md): Payments, analytics and the daily tools. Picks: Stripe, PostHog, GitHub.

## Related

- [Every layer of the stack](https://cloudlesslabs.com/stack/layers/index.md)
- [The whole stack in one file](https://cloudlesslabs.com/stack/brief.md)
- [Map of every Markdown file on cloudlesslabs.com, with what each one answers](https://ask.cloudlesslabs.com)