Errandy

A complex backend system demonstrating domain modeling, orchestration, distributed workflows, and reliability.

Errandy is a major backend project built to handle distributed workflows, process managers, idempotency, and event-driven architecture. It includes a ledger-only wallet model and a two-phase escrow flow, built around DDD and Enterprise Integration Patterns.

GitHub

AcceptApplicationProcessManager Flow

Payment  →  Accept  →  Assign  →  Escrow  →  Chat
       ↳ Correlated via shared correlationId
       ↳ Orchestrated by Saga / Process Manager
       ↳ Events retried via event retry queue

Tech Stack

NestJSTypeScriptGraphQLPrismaMongoDBRedisDockerNginxDigitalOcean

Key Features

Ledger-only wallet model and two-phase escrow flow
Saga/process-manager orchestration for distributed workflows
Strict layering and correlation IDs
Shared idempotency and event retry queue
GraphQL subscriptions for real-time updates
Error classification and reliability patterns

Engineering Challenges

Coordinating complex distributed processes like the AcceptApplicationProcessManager (payment → accept → assign → escrow → chat).
Managing eventual consistency and shared idempotency.
Handling event retries and failure states safely.
Refactoring core bounded contexts around DDD.

Key Learnings

Enterprise Integration Patterns and Saga orchestration.
Advanced TypeScript and NestJS architecture.
Designing complex wallet and escrow domains.
Implementing resilient event-driven infrastructure.