Evolution of Application Architecture: From Vertical Monolith to Microservices

As business scale expands, application architecture continuously evolves to address service transformation and governance, aiming to decouple service consumers and providers, increase reuse, improve reliability, and enhance team collaboration.

Four major stages are described:

1. Vertical monolithic ("vertical chimney") architecture, where a single WAR package contains all functionality.

2. RPC architecture, achieving logical front‑back separation (Spring MVC for the front end, RPC framework for back‑end services).

3. SOA architecture, introducing automatic service discovery, load balancing, autonomy, and orchestration.

4. Microservice architecture, an evolution of SOA with finer‑grained services, large service counts, agile delivery, and DevOps practices.

01 Vertical Architecture

This style appears in early, low‑traffic projects with single‑function business. It typically follows the classic MVC three‑tier model (view, controller, model) as shown in the diagram below.

mvc architecture model

The deployment typically looks like the following picture.

Deployment of vertical architecture

Characteristics: high maintenance cost, low deployment efficiency, poor team collaboration, reduced reliability (a single process failure can crash the whole node), and longer feature‑release cycles due to tight coupling.

02 RPC Architecture

RPC (Remote Procedure Call) enables calling remote services as if they were local, promoting service reuse. Popular open‑source RPC frameworks include Apache Thrift, Hadoop Avro‑RPC, Hessian, and Google gRPC (HTTP/2, protobuf). In Java, RPC relies on serialization, socket communication, dynamic proxies, and reflection.

The three main components are:

Service Provider – runs on the server, implements the service interface.

Service Publisher – registers the local service for remote invocation.

Local Service Proxy – runs on the client, forwards calls to the remote service and returns results.

RPC architecture deployment

RPC frameworks are simple, efficient, and generic, forming the technical foundation for SOA. However, they can make service configuration and load‑balancing management more difficult for consumers.

03 SOA Architecture

Service‑Oriented Architecture (SOA) is a coarse‑grained, service‑centric design. Common frameworks include Dubbo/Dubbox, HSF, DSF, Coral Service, and Spring Cloud. Dubbo is especially popular for distributed service development.

SOA application deployment

With a service registry, SOA provides automatic discovery, unified configuration, configurable routing, cluster fault tolerance, and comprehensive service governance (lifecycle, monitoring, security, fault location), greatly easing operations.

04 Microservice Architecture

Microservices further split services into finer granularity, leveraging containerization, agile delivery, and automated operations. The diagram below summarizes the key concepts.

Microservice architecture

In summary, the article presents a macro‑level overview of how application architecture has progressed from monolithic to microservice styles, setting the stage for deeper future explorations.