Real-time dashboard for a B2B FinTech

The legacy platform (jQuery + PHP) plateaued at 8 seconds of latency on consolidated reporting. Treasury teams lost a quarter of their morning waiting for exports.

ACPR compliance required a full audit: operation traceability, immutable logs, immediate access revocation. The legacy stack could never pass that bar without a rewrite.

Time-to-market for new financial products exceeded 6 months, leaving the FinTech uncompetitive against newer players.

Split into 3 tiers: a Next.js 15 front end (Server Components for authenticated SSR, client islands for the real-time charts), a typed tRPC API gateway, and the legacy system kept alive during the migration (strangler fig pattern).

Operations streamed over an authenticated WebSocket, automatic reconnection, client-side queue during disconnections. Server-side back-pressure to protect the PostgreSQL database.

Progressive route-by-route migration, blue-green deployment, feature flags to shift 1% → 10% → 100% of traffic onto the new platform over 8 weeks.

Compliance by design: append-only database logs, anti-tamper hash chain, rights segregation via PostgreSQL RLS, mandatory MFA for sensitive operations.

Latency divided by 12 (from ~8 s to ~650 ms on consolidated reporting), sub-second on individual operations.

Product time-to-market brought from 6 months to 3 weeks for new axes (a new product delivered end to end: spec → prod).

ACPR audit passed on the first attempt, with positive mention of the technical traceability. No major non-conformity.

Internal adoption: 100% of treasury teams migrated within 6 weeks, with no heavy training.