PlantUML Component Diagram: Microservices Architecture

Microservices Architecture with Component Diagrams

Component diagrams show the structural organization of a system in terms of its components and their interfaces. For microservices, each service is a component with defined API boundaries.

Basic Microservices Layout

@startuml
title Microservices Architecture

package "API Layer" {
  [API Gateway] as GW
  [GraphQL Federation] as GQL
}

package "Core Services" {
  [User Service] as US
  [Order Service] as OS
  [Product Service] as PS
  [Payment Service] as PAY
}

package "Supporting Services" {
  [Notification Service] as NS
  [Search Service] as SS
  [File Service] as FS
}

package "Data Stores" {
  database "Users DB\n(PostgreSQL)" as UDB
  database "Orders DB\n(PostgreSQL)" as ODB
  database "Products DB\n(MongoDB)" as PDB
  database "Search Index\n(Elasticsearch)" as ES
  queue "Message Broker\n(Kafka)" as MQ
  database "Object Storage\n(S3)" as S3
}

GW --> US
GW --> OS
GW --> PS
GQL --> US
GQL --> OS

US --> UDB
OS --> ODB
PS --> PDB
PAY --> OS

OS --> MQ : OrderCreated
MQ --> NS : consume
MQ --> SS : consume

SS --> ES
FS --> S3
PS --> ES : sync products

@enduml

Packages and Layers

Use package blocks to group services into architectural layers. Common layers include API Layer, Core Services, Supporting Services, and Data Stores.

Interface Notation

interface "REST API" as REST
interface "gRPC" as GRPC

[User Service] -up- REST
[User Service] -down- GRPC
[API Gateway] --> REST
[Order Service] --> GRPC

Interfaces show the communication protocol. This documents whether services communicate via REST, gRPC, GraphQL, or messaging.

Database Per Service

Each service in the diagram has its own database, which is the defining characteristic of microservices. The diagram makes this architectural decision explicit and visible.

Async Communication

Use queue components for message brokers. Label the arrows with event names to show what triggers each subscription.