From Monolith to Microservices: Why I Redesigned Finovara's Architecture - Finovara

At some point, a monolith starts working against you. In my case, Finovara was a single Spring Boot application handling everything (authentication, transactions, limits, piggy banks, notifications, activity logs, currency conversion) The bigger it got, the harder it was to change anything without worrying about something else breaking. So I broke it apart. This post is about the first three pieces I extracted: the API Gateway , the activity-log-backend , and a shared module called contracts-backend . The Old Structure Everything lived in one Spring Boot app. The activity log — which tracks everything a user does in the app (expenses added, limits changed, logins, account changes) — was tangled up with the core business logic. Adding a new type of activity meant touching the same codebase responsible for transactions, security, and everything else. The New Structure finovara-backend/ ├── api-gateway/ ├── activity-log-backend/ ├── contracts-backend/ └── core-backend/ Four modules (there will be more). Each with a clear responsibility. API Gateway The gateway is the single entry point for every request coming from the frontend. It runs on port 8888 with SSL enabled and uses Spring Cloud Gateway (WebFlux-based). Routing is simple and declarative: routes : - id : activity-log-backend uri : ${ACTIVITY_LOG_URL} predicates : - Path=/api/account-activity/**,/api/archive-activities/** - id : notification-backend uri : ${NOTIFICATION_BACKEND_URL} predicates : - Path=/api/notification-settings/** - id : core-backend uri : ${CORE_BACKEND_URL} predicates : - Path=/** Activity log routes go to activity-log-backend . Notification routes go to notification-backend . Everything else falls through to core-backend . The gateway also handles CORS centrally — https://localhost:5173 is the only allowed origin, with credentials support. No individual service needs to worry about CORS anymore. One thing worth noting: the gateway uses use-insecure-trust-manager: true for the HTTP client. Th