MERN Stack

A transactional email API for account verification, password resets, and notification emails, sent via Resend's official Node.js SDK from an Express 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 Express 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. An Express route signs a presigned URL with @aws-sdk/client-s3 and the s3-request-presigner package so the browser uploads straight to the bucket, and the keys stay in server environment variables. 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. An Express route signs a presigned URL with @aws-sdk/client-s3 and the s3-request-presigner package so the browser uploads straight to the bucket, and the keys stay in server environment variables. 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. An Express route signs a presigned URL with @aws-sdk/client-s3 and the s3-request-presigner package so the browser uploads straight to the bucket, and the keys stay in server environment variables. 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 store in front of MongoDB for the reads that repeat on every request: cached API responses, computed totals, and rate-limit counters. Express connects through ioredis or node-redis, and a rate limiter with a Redis store keeps limits consistent once the API runs on more than one instance. Railway and Render can both run a managed Redis next to the API. Add it when MongoDB queries become the slow part of a response, not before.

Express has no job queue of its own, so slow work such as sending emails or processing uploads either blocks a request or runs in a fire-and-forget promise that is lost if the process restarts. BullMQ is the standard Node.js answer: the API adds a job to a queue, a worker process runs it with retries and backoff, and repeatable jobs handle schedules. BullMQ stores its queues in Redis, so Redis comes with it; the instance used for caching can hold both.

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 Express API 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 Node SDK on the Express 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.