@startuml autonumber "<b>[0]" box "inner system" #Khaki database "Kafka" as k participant "Microservice" as ms database "PostgreSQL" as db end box box "vendor" participant "System" as ws end box ms -> k: kafka reading ms -> ms: some logic ms -> db: data save db -> ms: saving result ms -> ws: POST/... ms -> k: commit offset @enduml

This PlantUML diagram describes the sequence of interactions between components within the system:

1. The microservice reads messages from Kafka.
2. Performs some internal logic.
3. Saves data to PostgreSQL.
4. Retrieves the save result from the database.
5. Sends a POST request to an external (vendor) service.
6. After successful processing, commits the offset in Kafka.

This is a typical message processing scenario with guarantees of processing and state preservation, where:

• Kafka acts as a message broker.
• The microservice is responsible for business logic and interaction with the database and external systems.
• PostgreSQL is used for long-term data storage.
• The external system is a third-party service with which integration occurs.

This approach ensures reliability and data consistency during asynchronous event processing.