Case study · E-Commerce
Multi-vendor marketplace with UPI-ready checkout
A retail venture needed a multi-vendor marketplace for Indian buyers: fast storefront, UPI-first checkout, seller onboarding with commissions and payouts, and an admin hardened against fraud — delivered as a headless build the in-house team could extend.
Representative engagement · details anonymized under NDA
Project overview
- Client
- Retail marketplace venture (name withheld under NDA)
- Industry
- E-Commerce
- Services
- E-commerce Development, Next.js Development, API Security Testing
The problem
Off-the-shelf plugins could not model their commission slabs, COD-plus-UPI flows, and GST invoice requirements. Previous storefront attempts failed Core Web Vitals on budget Android devices, hurting conversion.
Requirements
- Headless storefront with sub-two-second loads on 4G
- UPI, cards, netbanking, EMI, and COD via Razorpay
- Seller dashboards with catalog, orders, commissions, and payouts
- GST invoicing and reconciliation exports
- Pre-launch checkout security review
Key challenges
- Complex commission and payout rules across vendor tiers
- Payment webhook reliability during network flakiness
- Bot-driven inventory hoarding during sale events
Our solution
- Built a Next.js storefront with ISR catalog pages served from the edge
- Implemented idempotent webhook handlers with reconciliation jobs for payments
- Added rate limiting, OTP abuse controls, and 2FA-enforced seller admin
- Ran a checkout-focused VAPT before launch and fixed all high findings
Technology stack
Security implementation
- Encrypted checkout with HSTS and strict transport policies
- Rate-limited OTP and login endpoints
- Seller admin with enforced 2FA and role separation
- Dependency scanning in CI for storefront and services
Performance considerations
ISR catalog, responsive image pipelines, and edge caching kept product pages fast on budget devices; load testing covered sale-day peaks.
Results
- Storefront launched with checkout security review completed pre-launch
- Seller onboarding and payouts operated without manual reconciliation
- In-house team took over feature development with documented handover
Lessons learned
- Idempotent payment handlers prevent the worst money bugs
- Edge-rendered catalogs beat client-rendered ones on real Indian networks
- Security review before launch is cheaper than incident response after
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