𝗥𝗲𝗮𝗰𝘁 + 𝗧𝘆𝗽𝗲𝗦𝗰𝗿𝗶𝗽𝘁 𝗶𝗻 𝟮𝟬𝟮𝟲: 𝗧𝗵𝗲 𝗣𝗮𝘁𝘁𝗲𝗿𝗻𝘀 𝗧𝗵𝗮𝘁 𝗔𝗰𝘁𝘂𝗮𝗹𝗹𝘆 𝗦𝗰𝗮𝗹𝗲

Most React + TypeScript codebases don’t fail because of bad syntax, they fail because the architecture doesn’t scale.

Here are the patterns that actually scale — and the ones that quietly kill teams.

1 — Feature‑First Modules, Not Tech‑First Folders
If your app is still structured like this:

• components/
• hooks/
• utils/
• pages/ …you’re already in trouble.

Scaling teams need feature‑first boundaries:

• trading/
• positions/
• orders/
• analytics/

Each with:
its own components
its own hooks
its own types
its own tests

Pattern that scales: feature‑sliced architecture.
Pattern that dies: “shared” everything.

2 — TypeScript as a Domain Language, not a Safety Net
Most teams use TypeScript like this:
Let’s just add types so it doesn’t crash.
Senior teams use it like this:
Let’s model the domain so it can’t lie.
That means:

• OrderSide = BUY | SELL
• OrderStatus = PENDING | FILLED | CANCELLED | REJECTED
• Price = Branded
• Quantity = Branded

You’re not just avoiding bugs.
You’re encoding business rules into the type system.
Pattern that scales: domain‑driven types.
Pattern that dies: any, unknown, string | number | null.

3 — State Management as Scope, Not as Tool War
Redux vs Zustand vs Context vs Signals vs Whatever‑Is‑New‑This‑Week.
None of that matters if you don’t answer one question: What state belongs where?
Patterns that scale:

• local UI state → useState / useReducer
• feature state → feature store (Zustand/Redux/etc.)
• app‑wide state → global store (auth, theme, user)
• server state → React Query / RTK Query / custom cache

Pattern that scales: state by scope.
Pattern that dies: “just put it in global state”.

4 — Pub/Sub over Prop Drilling and Global Mess
As apps grow, everything wants to talk to everything.
The naive solution:

• pass props down 5 levels
• or throw everything into a global store The scalable solution:
• events
• pub/sub
• domain‑level channels Example:
• order:created
• order:updated
• position:closed
• price:stream:spike

Components react to events instead of being tightly coupled.
Pattern that scales: event‑driven UI.
Pattern that dies: “just pass it down”.

5 — Tests as Contracts, Not as Comfort Blanket
Saying “In 2026, we have tests” is meaningless.

What matters is:

• Do your tests lock in behaviour that matters?
• Do they describe domain rules, not implementation details?
• Can a new engineer change a component without breaking 50 brittle tests?

Patterns that scale:

• test behaviour, not internals
• test contracts, not implementation
• test critical flows, not every line

Pattern that scales: tests as living documentation.
Pattern that dies: 100% coverage as a vanity metric.

The Punchline
React + TypeScript is about boundaries, domain‑driven types, scoped state, events, and tests that describe behavior.

𝗪𝗿𝗶𝘁𝘁𝗲𝗻 𝗯𝘆 𝗥𝗶𝗰𝗮𝗿𝗱𝗼 𝗦𝗮𝘂𝗺𝗲𝘁𝗵