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How much faster is building internal tools with Claude?
By Vaibhav Vijay ·
Short answer: About two days instead of an estimated three to four weekends, for the first version of Ekatra's invoice tracker: the dashboard, logins and OCR pipeline, built with Claude as a pair programmer. It replaced a Google Sheet in April 2026 and runs for about ₹470 a month.
What got built in two days?
First version of the Ekatra invoice tracker, April 2026
| Part | What it does |
|---|
| Dashboard | Six pages with KPIs, ageing buckets and top debtors |
| Logins | Email and password accounts for the team |
| OCR pipeline | Reads invoice PDFs dropped in the team's WhatsApp group |
| Build time | About 2 days, against 3 to 4 weekends estimated by hand |
What did Claude not replace?
Judgement about data. In August 2026 the team reported a ₹423 invoice showing as ₹9.5 crore: the extractor had read the 8-digit HSN product code as the total. The fix was a rule a person had to choose, that every amount must match the amount-in-words line. Re-checking every invoice against its PDF fixed 2 rows and restored 6 lost invoices.
Which habits kept fast building safe?
- New features go in new files, leaving working code untouched
- Every feature ships with a rollback path, such as a tagged stable version
- Features are proven in production with throwaway test data, then deleted
- Human edits outrank machine input: a re-scan can never overwrite a correction
Related questions
Which Claude model was used?
Claude Sonnet 4.5, as a pair programmer.
Does it need a developer to keep it running?
No. It runs unattended on Cloudflare and one small server, and the repo holds the project's history and reasoning so any engineer or AI assistant can pick it up.
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