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Fintech for Startups
Playbooks and case studies covering fintech for startups.
What KYC Actually Requires of Your Product in the UAE
A document upload wired to a third-party API is not KYC — it's one control inside a system the CBUAE now expects you to run continuously. Here's what the regulator actually requires of your product architecture, and where founders get caught short.
What Audit Trails Actually Require of Your Software
Your application logs are not an audit trail. Here is what RBI's ITGRCA, SEBI's system audit framework, and the Companies Act actually require of the software — and where most Series A fintechs fail the review.
Idempotent Webhooks: Handle Retries Without Duplicate Orders
A backend engineer's tutorial for building idempotent webhook handlers that survive Stripe or Razorpay retries. The fix is not deduplicating on event ID — it's collapsing the write and the ack into one atomic unit.
How GimBooks Scaled GST Filing to 3M Users Without Breaking
A deep look at the architectural decisions that let GimBooks scale GST filing to millions of Indian SMB users. The real bottleneck was not compute — it was stateful rule evaluation across a financial year.
Idempotent Webhook Handlers: Stop Processing Events Twice
If your Stripe or Razorpay webhook occasionally double-credits a wallet or creates duplicate orders, the fix isn't deduplicating HTTP requests — it's making the database write itself a no-op on replay. Here's a runnable tutorial that shows how to do it correctly under concurrent retries.
GST Compliance Cheatsheet for SaaS Products Serving Indian SMBs
A reference sheet for SaaS founders whose billing engine treats GST as one flat tax field. Covers the four axes GST branches on — and the invoice fields that make or break your customers' input tax credit claims.
How GimBooks Scaled GST Filing to 3M Users Without a DBA
GimBooks handled normal load fine but crashed every GST deadline cycle. Here's the architectural call that fixed it — and why horizontal scaling alone would have made the problem worse.
What Is Idempotency? Stop Charging Customers Twice
A double-charge after a mobile timeout is almost always a retry bug, not a payment gateway bug. Here's how idempotency keys work, and why the fix lives in your client — not your server.
How GimBooks Served 3M Users Without Breaking GST Logic
A walkthrough of how the GimBooks accounting SaaS handled GST edge cases at scale by treating compliance as a state machine, not a calculation library. The lesson generalizes to any fintech whose rule logic works at 50K users but silently breaks at 500K.
How GimBooks Kept AI Accurate Across 3M Downloads
When an AI bookkeeping feature works at 10K users but breaks at 500K, the instinct is to blame data volume. The GimBooks case study shows the real culprit is usually segment collapse — and the fix is architectural, not statistical.
Feature Stores Explained: Why Your AI Keeps Training on Lies
Your credit-scoring model passes every offline test, then degrades two weeks after deployment. The culprit isn't drift — it's that your training pipeline and your serving pipeline are computing features differently, and no one is enforcing they match.
How KarroFin Scored 250K Users Without a Credit Bureau
KarroFin's underwriting model was rejecting creditworthy borrowers for the wrong reason: absence of bureau data. Here's the engineering call that fixed it, and why chasing the bureau score is the wrong target for any lender serving thin-file users.