Building a Fintech Platform Solo: 185 Tables, 69 APIs, 7 Systems

Most engineers work on one service at a time. I built an entire ecosystem.

The Nexural platform started as a simple idea: a dashboard for my trading community. It became a full fintech platform with 185 database tables, 69 API endpoints, Stripe billing, an AI-powered Discord bot, a research engine, a newsletter studio, and a real-time alert system.

I designed and built all of it. Here's what I learned.

The Scope

Seven interconnected systems:

1. Trading Dashboard — real-time market data, charts, portfolio tracking
2. Discord AI Engine — 30+ commands, GPT-4o integration, auto-moderation
3. Research Engine — 71+ metrics, strategy analysis, CSV import
4. Alert System — NinjaTrader 8 integration, .NET backend, real-time notifications
5. Newsletter Studio — automated content generation and distribution
6. Strategy Tracker — performance monitoring across trading systems
7. Automation Suite — 61 test suites, CI/CD, quality gates

Database Design at Scale

185 tables sounds intimidating. The key was phased design:

• Phase 1 (Core): Users, auth, subscriptions — 20 tables
• Phase 2 (Trading): Instruments, positions, signals — 35 tables
• Phase 3 (Community): Discord integration, moderation logs — 25 tables
• Phase 4 (Analytics): Metrics, reports, telemetry — 30 tables
• Phase 5-7: Research, alerts, newsletter — 75 tables

Each phase had its own migration, its own test suite, and its own rollback plan. I never modified more than one domain at a time.

Schema Decisions That Mattered

Normalized where it counts: User → Subscription → Plan is fully normalized. No denormalization shortcuts that would create billing bugs.

Denormalized where speed matters: Trading dashboards query denormalized views. A trader doesn't care about 3NF — they care about sub-50ms load times.

Row-level security everywhere: Supabase RLS policies on every table. A user can never see another user's data, even if the API has a bug.

API Architecture

69 endpoints following consistent patterns:

GET    /api/v1/instruments          — list with pagination
GET    /api/v1/instruments/:id      — detail
POST   /api/v1/instruments          — create (admin)
PATCH  /api/v1/instruments/:id      — update (admin)
DELETE /api/v1/instruments/:id      — soft delete (admin)

Every endpoint has:

• Zod schema validation on input
• Rate limiting (per-user, per-endpoint)
• Structured error responses
• Full test coverage

Stripe Integration

Billing is where fintech gets real. I implemented:

• Subscription lifecycle (create, upgrade, downgrade, cancel)
• Webhook handling for payment events
• Dunning for failed payments
• Prorated billing on plan changes
• Invoice generation

The Stripe webhook handler alone is 400 lines of carefully tested code. Payment bugs are the kind that lose customers permanently.

What I'd Do Differently

1. Start with a monorepo. I split services too early. A monorepo with shared types would have saved weeks of type synchronization.
2. API versioning from day one. I added /v1/ after breaking two integrations. Should have been there from the start.
3. Less custom, more conventions. I built custom auth middleware when NextAuth would have been fine for v1.

The Real Lesson

Building a platform solo teaches you something that team environments don't: every decision compounds. Good architecture decisions save you hundreds of hours later. Bad ones haunt you at 2am.

The Nexural ecosystem works because I spent more time designing than coding. The schema document was 40 pages before I wrote the first migration.

If you're building something ambitious alone, invest in architecture first. The code is the easy part.