Case Study

Architecting a Modular KYC Microservice Platform

Spring Boot · Next.js/React · Android · FastAPI KYC · OCR/vision modules

Executive Summary

Designed and implemented a modular platform spanning backend, web, mobile, and a FastAPI KYC service. This case study documents service boundaries, check policy, and review states; no population-level accuracy or false-rejection outcome is published without labeled evaluation evidence.

The Problem

Keep upload ownership, KYC case state, and component checks explicit across service boundaries
Keep web and Android clients aligned with the Spring API without moving authorization into the clients
Represent check thresholds and review outcomes without presenting them as measured population results

Architecture & Approach

1
Domain-oriented Spring Boot modules (auth, accounts, analytics, kyc, wallet)
2
FastAPI KYC service: face, liveness, OCR, document-classification checks, and an aggregate policy
3
Spring orchestration: bounded file reads, persisted check records, and UNDER_REVIEW fallback on service failure
4
Android Wallet: card reload, QR pay, and bill-pay intent flows through Retrofit interfaces and DTOs
5
Next.js web client with role-gated routes, bearer-token requests, and account flows

Challenges & Trade-offs

KYC service failure → persist an error check and move the case to UNDER_REVIEW rather than approving it

Upload integrity → require four distinct owned uploads with the expected document categories

Model boundary → keep optional ONNX/Tesseract modules distinct from the current simple default factory path

Outcomes & Results

Implemented explicit KYC upload, case, check, and status boundaries in the reviewed source
Implemented APPROVE, UNDER_REVIEW, and REJECT policy branches with reason codes and per-check records
Accuracy, false-rejection rate, manual-review volume, and production outcomes remain unmeasured in the reviewed evidence