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Christopher
Christopher

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Building an API-First Personal Finance Platform: 12 Years and Lessons in Shipping vs. Perfecting

#api #webdev #fintech #startup

After 12 years of development, I'm launching Trupocket - an API-first personal finance platform. Here's the journey and hard lessons about shipping vs. perfecting.

The Vision

Every personal finance app (Mint, YNAB, Monarch Money) is a closed system. No APIs. No developer access. Forced processes and workflows.

I wanted to build the infrastructure layer - the "AWS of personal finance" - where developers can build financial tools without rebuilding the core ledger. A system that doesn't get in the way with managing your finances and understanding truly what is in your pocket.

What I Built

Core API Features:

  • Dozens of RESTful endpoints
  • OAuth 2.0 authentication
  • Multi-tenant household architecture
  • Real-time balance calculations
  • Categorization with budget tracking
  • Scheduled transaction automation
  • Financial reports and forecasts

Resources Available:

  • Accounts (checking, savings, credit cards)
  • Transactions (with split categorization)
  • Categories and budgets
  • Payees
  • Scheduled transactions
  • Hashtags for flexible organization
  • Financial reports

Performance Targets:

  • <200ms average API response time
  • Real-time balance updates
  • Concurrent transaction handling

API-First Design Philosophy

1. Developer Experience First

Every endpoint has:

  • Clear, consistent naming
  • Comprehensive documentation
  • Request/response examples
  • Detailed error messages with error codes
  • Proper HTTP status codes

2. OpenAPI/Swagger Documentation

Interactive API docs with:

  • Live testing interface
  • Complete schema definitions
  • Authentication examples
  • Error response patterns

3. Multi-Tenancy Done Right

"Households" provide:

  • Isolated tenant data
  • Shared access for families/businesses
  • Multiple households per user
  • Proper security boundaries

The Perfectionism Problem

I have always struggled with perfectionism when I build software. I always continue to want to perfect and build and re-build.

Here are some of the traps I ran into over the years in building this software:

Trap 1: Endless Refactoring (biggest challenge)

Always would find a better way to build/write the code, so would spend huge chunks of time refactoring working code. Yet, these changes are architectural perfect; the changes added zero user value.

There were some episodes where I throw away a near-ready product and start over because "I can build it better". Additionally, this constant refactoring caused major burnout. So then I would go into a hibernation from working on it, causing more delays.

Then I would come back after that burnout break, and then perpetuate the cycle and refactor more because things are out-of-date after the break.

Fix: "Is this a launch blocker?" became my mantra.

Trap 2: Tool Optimization

Built automation tools, then spent huge chunks of time optimizing THE TOOLS.

Fix: Tools are done when they work, not when they're perfect.

Trap 3: Architecture Debates

Months deciding between technical approaches.

Fix: Pick one, ship it, migrate later if needed.

Anti-Perfectionism Rules

  1. SHIP FIRST, OPTIMIZE LATER
  2. GOOD ENOUGH IS PERFECT
  3. USER VALUE OVER CODE BEAUTY
  4. TIME-BOX PERFECTIONISM (20% max)
  5. NO PREMATURE OPTIMIZATION

What I'd Build Differently

Should have done:

  • Automated database migrations earlier
  • Built admin dashboard sooner
  • Added monitoring/metrics from start
  • Started with comprehensive integration tests

Glad I did:

  • Focused on API documentation quality
  • Built multi-tenancy from day 1
  • Prioritized performance from the start
  • Created clear anti-perfectionism guidelines

The Business Model

  • Free Tier: Limited accounts/transactions
  • Premium: $2.99/month (vs. $15+ competitors)
  • Developer: $29.99/month, 10K API calls/day

Strategy: Be the infrastructure layer. Let developers build on top.

What's Next

Immediate:

  • User-friendly web app
  • AI/ML integrations
  • More household styles
  • Webhook events
  • Mobile apps

Long-term:

  • Developer SDKs (TypeScript, Python, Go)
  • Investment tracking
  • More account types
  • Tax optimization features
  • Bank connectivity (Plaid integration)
  • Open Banking compliance

Try It

API: https://api.trupocket.app
Swagger: https://api.trupocket.app/docs
Docs: https://api.trupocket.app/docs/getting-started

Questions? Ask in comments.

What would YOU build with a personal finance API?

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