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2 min read Backend

init commit: Factories, Spreadsheets, and AWS Scars

init commit: Factories, Spreadsheets, and AWS Scars
"Every SaaS begins with a friend's complaint and an Excel sheet that looks like a war crime."

The Spark

A good friend works in automotive as a process engineer. His life revolves around efficiency, takt time, and Yamazumi charts — stacked bar charts showing how tasks are spread across operators.

One evening, over coffee, he showed me their tool. It wasn't a tool. It was Excel.

  • Dozens of tabs
  • VBA macros duct-taped together
  • Cells with formulas only wizards can decipher
  • Filenames like yamazumi_final_v12_REALLY_FINAL.xlsx

Factories run on lean, but their line balancing tool was anything but lean.

That's when I thought: what if I built them something real?

Firebase & Supabase: The Good, the Bad

Firebase and Supabase are excellent tools. Free tiers to get you off the ground, integrated auth, ship an MVP in days.

But for an enterprise SaaS with multi-tenant auth, audit logging, and compliance needs — the free tier disappears fast, vendor lock-in becomes real, and auditability becomes a problem.

For a quick MVP, they're gold. For factories and compliance-heavy SaaS, they fall short.

AWS: The Hacker's Pain, the Startup's Gain

AWS is notorious for complexity, but as a solo dev with no revenue, the math works:

  • AWS Free Tier — 12 months of free usage on core services
  • $200 starter credit — on account creation
  • AWS Activate Founders — $1,000 in credits + $350 in support credits

Why App Runner

When you build a SaaS MVP, you don't want to spend three weekends wiring up networking. App Runner is AWS saying: "You focus on your container, we'll handle the plumbing."

  • Zero-to-scale: Scales down to zero when idle — not paying for idle containers
  • Batteries included: Load balancer, VPC, HTTPS, health checks, auto-scaling
  • Code focus: Push Docker image → App Runner runs it
  • Cost-effective: Under $20-30/month with low traffic (free with credits)

The Stack

# frontend
React + TypeScript + Vite + Tailwind
Zustand, AWS Amplify, Netlify

# backend
Spring Boot 3.2 + Kotlin + JDK 21
OAuth2 Resource Server + JWT
Docker + Gradle

# infra
AWS App Runner, RDS PostgreSQL
AWS Cognito, Terraform (state in S3)
CI/CD with GitHub Actions

Future-Proofing

App Runner isn't a dead end. Everything is containerized — images in ECR, CI/CD in GitHub Actions. If traffic spikes, I can point those same Docker images at ECS or EKS. Speed now, flexibility later.

Lessons

  • Free tiers are awesome — until you need the one feature that pushes you into paid.
  • AWS looks expensive, but credits + free tier can cover most of year one.
  • Pick enterprise-grade early; you'll swear more now but save rewrite pain later.
  • Document every decision like a commit message. Future-you will need it.

Published by:

Ercan