Full-Stack Architecture

Full-Stack Architecture

Every production application you have ever used — from Instagram to your bank's mobile app — is built on the same fundamental architecture: a client that renders UI, a server that processes logic, and a database that persists state. What varies is where each responsibility lives, how they communicate, and how the system handles failure.

The Modern Stack

In 2024, the dominant full-stack pattern for product companies is: Next.js or Remix on the frontend/BFF (Backend for Frontend) layer, a PostgreSQL database (usually managed via Supabase or PlanetScale), and a combination of API routes and serverless functions handling business logic. This is not the only valid architecture, but it is the one you will encounter most often when joining or auditing a team.

Next.js is worth understanding deeply because it operates at multiple layers simultaneously. A single Next.js application can serve:

• Static pages — HTML generated at build time, served from a CDN, essentially free at scale
• Server-rendered pages — HTML generated per-request on a server, necessary when content is personalized or real-time
• Client components — JavaScript that runs in the browser for interactivity
• API routes — Server-side endpoints at /api/* that handle form submissions, webhooks, and data mutations

How a Request Flows

When a user visits your app, this is what happens in under 200ms on a well-optimized system:

1. Browser sends a GET request to your domain
2. DNS resolves to a CDN edge node geographically near the user
3. If the page is static and cached, the CDN returns it immediately — no server involved
4. If SSR is required, the edge node forwards the request to a serverless function
5. That function queries the database, renders the HTML, and returns it
6. The browser displays the HTML, then downloads the JavaScript bundle
7. React hydrates the page — attaching event handlers to the static HTML
8. Subsequent interactions can happen client-side or trigger API calls

The critical insight: network round-trips are your biggest performance cost. Every database query, every API call, every redirect adds latency. Architects obsess over reducing round-trips and moving compute closer to users.

The Database Layer

Your database is the source of truth. Everything else can be rebuilt from it. This is why experienced engineers treat schema design as the highest-leverage decision in the early life of a product — a bad schema is expensive to fix once you have production data.

Most product databases are relational (PostgreSQL, MySQL). They store data in tables with typed columns, enforce relationships via foreign keys, and support complex queries via SQL. For read-heavy workloads, you add a caching layer (Redis) that keeps frequently-accessed data in memory so the database is not hit on every request.

What "Serverless" Actually Means

Serverless does not mean no servers — it means servers you do not manage. Your code runs in a container that spins up on demand, executes, and disappears. You pay per invocation rather than per idle hour. This is excellent for variable-load APIs and background jobs, but terrible for long-running processes or workloads that need persistent memory.

Choosing an Architecture

The right architecture is the simplest one that handles your current load with room to grow. A startup with 500 users does not need microservices. A single Next.js app with a managed database handles millions of monthly active users without heroics. Premature architectural complexity kills more startups than technical debt does.