Python Web (FastAPI + React)

A hosted identity platform with an official Python SDK for verifying tokens in FastAPI route dependencies; it handles social logins, MFA, and session management without building an auth service yourself.

Supabase's standalone auth service, usable from FastAPI even without adopting the rest of Supabase, a lighter-weight option if you just need email/password and OAuth logins backed by a hosted user table.

A transactional email API for account verification, password resets, and notification emails, sent via Resend's official Python SDK from a FastAPI route handler in a few lines of code, with a free tier for getting started.

The established high-volume choice, with dedicated IP addresses and deliverability tooling for apps sending at serious scale. No permanent free plan (a 60-day trial, then paid tiers), so it earns its slot when volume and deliverability matter more than upfront cost.

An all-in-one platform combining the transactional email API with marketing campaigns, a built-in CRM, and SMS from the same dashboard. A permanent free tier of 300 emails a day with no card required makes it an easy starting pick for an early-stage app.

Adds subscription billing, one-time checkout, and invoicing via Stripe's hosted Checkout or embedded Elements, with FastAPI handling webhook verification and API calls server-side. The stack works fully without it; add this once the product is ready to charge for something.

Utility-first CSS that pairs naturally with React's JSX: classes go directly on elements with no separate stylesheet to maintain. The stack ships with plain CSS by default; add this if you'd rather not hand-write it.

S3-compatible object storage with no egress fees, so serving uploads, images, and exports costs only for storage and operations. A FastAPI route creates a presigned upload URL with boto3 so the React app sends the file straight to the bucket, and the keys stay in the API's environment. The 10 GB free tier covers an early product.

The reference object store and the API the others copy, with the most storage classes, regional controls, and lifecycle rules. A FastAPI route creates a presigned upload URL with boto3 so the React app sends the file straight to the bucket, and the keys stay in the API's environment. It fits best when the rest of the app already runs on AWS, though data transfer out is billed.

An S3-compatible store at roughly a third of S3 Standard's storage price, a fit for backups and large media libraries. A FastAPI route creates a presigned upload URL with boto3 so the React app sends the file straight to the bucket, and the keys stay in the API's environment. Egress is free up to three times the stored data, and a CDN in front of a public bucket covers heavier delivery.

An in-memory cache for the FastAPI backend, reached through redis-py's asyncio client so lookups never block the event loop. fastapi-cache2 caches whole endpoint responses with a decorator, and a Redis counter gives rate limiting that holds across every Uvicorn worker. The same instance can serve as a Celery broker if background jobs come later. PostgreSQL already keeps frequently read rows in memory, so add Redis when repeated queries start to dominate response time.

FastAPI's BackgroundTasks cover a quick job after a response, but they run inside the API process and vanish if it restarts. Celery moves that work to separate worker processes: a route calls delay() on a task such as an export or a webhook delivery, the React app polls the task's state, and failed runs retry with backoff. Celery beat handles schedules. It needs a broker, usually Redis (the instance used for caching can serve both), or RabbitMQ for stricter delivery.

Runs the test suite and triggers deployments on every push, directly from the same GitHub repo the code already lives in, with no separate CI service to configure.

GitLab's built-in CI/CD system, configured via .gitlab-ci.yml in the repository, the natural pick if the project's code lives on GitLab (self-hosted or gitlab.com) rather than GitHub, with the same YAML-pipeline model as GitHub Actions.

Packages the FastAPI backend into a container image for consistent local development and deployment, independent of the hosting platform chosen above; the React frontend still just builds to static assets and doesn't need one.

Error tracking and performance monitoring with dedicated SDKs on both sides (Sentry's React SDK on the frontend, its FastAPI integration on the backend), giving stack traces across the full request path. Open-source with a self-hosted path, alongside its own managed cloud.

A broader observability platform covering APM, infrastructure metrics, and log management in one dashboard, useful once a team is already running other services worth monitoring alongside this app. Managed-only, with pricing that scales by host and usage rather than Sentry's per-error volume.

An all-in-one product analytics platform: event tracking, session replay, feature flags, and A/B testing in one SDK. The richest feature set if you want more than pageviews.

The industry-standard, free analytics platform, with native Google Ads and Search Console integration. Requires a cookie consent banner in most jurisdictions (GDPR/CCPA), and all data lives on Google's infrastructure, the tradeoff the other three picks were built to avoid.

A lightweight, privacy-first analytics tool with no cookie banner required. A good fit for simple traffic metrics without PostHog's broader feature surface.

Open-source and self-hostable, keeping analytics data on infrastructure you control. Pairs naturally with the self-hosted Hetzner hosting option above if you want to avoid a third-party analytics vendor entirely.