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Data Migration—2025—3 weeks
FINTECH CO
A financial services company drowning in Excel hell needed to be rescued before their business drowned with them.
PostgreSQLPythondbtRetool
🪓KILLED: 47 spreadsheets
THE DISEASE
Finance team managing $50M+ through 47 interconnected Excel spreadsheets. One guy knew the formulas. He quit. VLOOKUP chains that made grown engineers weep.
✕47 spreadsheets with circular dependencies
✕No version control - "final_final_v3_REAL.xlsx"
✕Monthly close took 2 weeks
✕One typo once cost them $200k
✕The formulas had formulas
THE SURGERY
01
Autopsy
Mapped every single spreadsheet relationship. Found 3 that nobody knew existed but were critical.
02
Data Model
Designed a normalized PostgreSQL schema that actually made sense to humans.
03
Migration
Built Python ETL pipelines to move 5 years of data without losing a single cell.
04
Interface
Built Retool dashboards that made finance actually excited about their jobs.
THE AFTERMATH
From Excel chaos to a system that practically runs itself. The CEO called it "the best money we ever spent."
Monthly close time
2 weeks→2 days
Data sources
47 spreadsheets→1 database
Error rate
~5%→0%
Finance team happiness
😭→😎
"
I used to have nightmares about spreadsheets. Now I just have regular nightmares.
Head of Finance
Fintech Co