Full-stack architecture
Flutter + Spring Boot: Complete Architecture Guide
Flutter + Spring Boot: Complete Architecture Guide requires decisions about Flutter clients, Spring Boot domain services, OAuth or token flows, PostgreSQL, push notifications and API versioning. This guide explains the architecture, delivery and production practices needed to achieve a mobile architecture combining one cross-platform UI with a strongly structured Java backend.
Build Flutter around features and states
Group presentation, application state and data access by feature. Model loading, empty, refreshing, failure, offline and success states explicitly so the interface can recover from real network conditions.
Hide HTTP and local storage behind repositories, keep platform secrets out of the bundle and test the critical journey with production builds on representative devices. State-management package choice is less important than clear ownership and testable transitions.
Version the mobile-to-backend contract
Installed mobile versions remain active after the backend changes. Prefer additive API changes, stable field meanings and an explicit supported-version policy; introduce a new contract when a breaking change cannot be avoided.
Use runtime validation on both sides, consistent error codes and request identifiers. Test older supported apps against new backend releases before removing a field or changing workflow behavior.
Use Spring Boot modules around business capabilities
Organize code by domains such as identity, billing or fulfillment rather than placing every controller, service and repository in global folders. Keep transaction boundaries and dependencies explicit so modules can change without reaching through one another.
Start with a modular monolith unless independent deployment solves a measured team or scaling problem. Spring Boot already provides production conventions; adding distributed services too early multiplies configuration and failure modes.
Secure Spring Boot with explicit authorization
Configure Spring Security with a deny-by-default filter chain and test public, authenticated and privileged routes. Validate token issuer, audience and expiry, then enforce resource ownership or method authorization instead of trusting roles sent by a client.
Define CORS precisely, decide whether CSRF applies to the authentication model, keep secrets outside source control and avoid exposing sensitive Actuator endpoints. Return safe errors and log security events without recording credentials or tokens.
Transactions, JPA and PostgreSQL
Keep transactions short and aligned with business operations. Inspect the SQL generated by the ORM, avoid N+1 loading, page large results and use database constraints for invariants that must survive concurrent requests.
Add indexes from real query predicates and ordering, then confirm plans with EXPLAIN. Configure the connection pool against database capacity; increasing application instances must not create more connections than PostgreSQL can support.
Deploy frontend and backend independently
Build immutable artifacts, promote configuration through environments and run database migrations as a controlled step. Contract compatibility lets clients and servers release on different schedules without coordinated downtime.
Collect structured logs, metrics, traces, crashes and performance signals. Share request identifiers across the client and backend so support can connect a visible failure to its server-side cause.