Sekiban Event Sourcing Framework

The Sekiban DCB CLI tool is designed for managing projection states, inspecting events, and working with local SQLite caches. It is primarily used for:

• Building and rebuilding multi-projection states.
• Debugging by inspecting events and projection states.
• Managing local SQLite caches to enable offline development.
• Environment management via multi-profile configurations (e.g., dev, staging, production).

The Sekiban.Dcb.DynamoDB package provides an Amazon DynamoDB event store implementation for the Sekiban.Dcb framework. It is designed to maintain API parity with the existing Cosmos DB provider while leveraging DynamoDB-specific features for performance.

Key Requirements for Large States: Because DynamoDB has a 400 KB item size limit, any projection states exceeding ~350KB must be offloaded to S3. To support this, you must use the Sekiban.Dcb.BlobStorage.S3 package alongside the DynamoDB implementation.

The Commands Module provides the utilities necessary for executing commands within the Sekiban TypeScript ecosystem. It consists of three primary components:

• unified-executor.ts: The command executor designed to work with schema-based commands.
• validation.ts: Utilities for validating command input against their defined schemas.
• types.ts: Basic type definitions for command execution options.

Sekiban is an application development framework leveraging Event Sourcing and CQRS (Command Query Responsibility Segregation). It is built using C# .NET Core 7+ and provides a declarative API for creating event-sourced applications.

Key characteristics:

• Event Store Support: Supports various event stores including Microsoft Azure Cosmos DB and Amazon DynamoDB.
• Cloud Native: Designed for easy deployment on Azure or AWS.
• Developer Focus: Aims to allow developers to focus on business logic by providing tools for commands, events, projections, and testing, rather than managing the underlying event-sourcing infrastructure.

The Sekiban TypeScript ecosystem is divided into the core framework and several provider/integration packages:

• @sekiban/core: The central framework implementing event sourcing and CQRS patterns.
• @sekiban/postgres: Storage provider for PostgreSQL.
• @sekiban/cosmos: Storage provider for Azure Cosmos DB.
• @sekiban/dapr: Integration for Dapr actors with snapshot support.

The current implementation of Materialized Views in Sekiban supports the following runtime configuration:

• Supported DB Backends: PostgreSQL, SQL Server, MySQL, and SQLite.
• Execution Host: Orleans.
• Event Source: Existing DCB event stores resolved by ServiceId.

In a typical sample implementation (e.g., DcbOrleans.WithoutResult.ApiService), the architecture consists of:

• A Postgres instance for the Event Store.
• A separate Postgres connection for managing Materialized View tables.
• Orleans managing status, buffering, and refresh logic.

The sekiban-orleans-aspire template generates a multi-project solution organized as follows:

• [ProjectName].Domain: Contains the core domain models, events, commands, and queries.
• [ProjectName].ApiService: Provides API endpoints for executing commands and performing queries.
• [ProjectName].Web: A Blazor-based web frontend.
• [ProjectName].AppHost: The .NET Aspire host used to orchestrate all services.
• [ProjectName].ServiceDefaults: Contains common service configurations used across the solution.

The Sekiban TypeScript ecosystem is organized into scoped npm packages under the @sekiban/* namespace. The planned package structure is:

• @sekiban/core: The main framework functionality (equivalent to Sekiban.Pure).
• @sekiban/dapr: Integration with Dapr (equivalent to Sekiban.Pure.Dapr).
• @sekiban/testing: Test utilities for the framework.
• @sekiban/cosmos: Integration with Azure Cosmos DB.
• @sekiban/postgres: Integration with PostgreSQL.

Sekiban DCB supports multiple storage providers across Azure and AWS. Use the following matrix to plan your architecture: