FastAPI + Supabase + HTMX

A transactional email API for account verification, password resets, and notification emails, sent via Resend's official Python SDK from a FastAPI route handler, 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.

A utility-class CSS framework: styles are composed directly in markup via class names instead of writing separate stylesheet files. The default styling choice bundled by most modern framework CLIs (create-next-app, create-vue, the SvelteKit and Astro starters all offer it), and the base layer shadcn/ui components are built on when that's loaded into the catalog in the future.

Ready-made components and a grid for Jinja2 templates served by FastAPI, added with a CDN link and no build step. Bootstrap's data-attribute components such as modals and dropdowns keep working on content swapped in by HTMX, while tooltips and popovers need initialising after a swap. Pick it or Tailwind, not both.

Alpine.js adds lightweight, declarative client-side interactivity on top of this stack's HTMX-driven FastAPI pages: toggling a mobile menu, showing a modal, or switching an active tab, all without triggering a server round trip HTMX would otherwise need. It is included via a script tag, with behavior written as HTML attributes (x-data, x-show, x-on) rather than a build step, keeping the stack's zero-bundler approach intact.

A cache for the HTML fragments HTMX requests over and over, such as counters, lists, and sidebars that change rarely, so FastAPI can return them without a round trip to Supabase. redis-py's asyncio client handles it inside async routes, and the same Redis keeps rate-limit counters. Supabase's Postgres already serves hot rows from memory, so add Redis when repeated fragment renders or database calls begin to slow pages down.

Slow work behind an HTMX page, such as processing an upload or sending a batch of emails, can run in Celery workers instead of the request. FastAPI's BackgroundTasks are the lighter choice for one quick job, and Supabase Queues stores messages in the database but leaves consuming them to your code. Celery brings the workers, retries, and schedules, and an element can poll a status route until the task finishes. Its broker is usually Redis, shared with caching.

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 whole FastAPI + HTMX app into a container image for consistent local development and deployment, independent of the hosting platform chosen above.

Error tracking and performance monitoring with Sentry's dedicated FastAPI integration, covering both route handlers and template rendering. 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.