Contracts
Versioned APIs with input validation and idempotency for write operations.
All solution studies
Backend & Data
An Integration Layer That Unifies Systems Without a Big-Bang Rewrite
A backend solution study connecting sales, billing, inventory, and messaging through explicit contracts and reliable data flow.
Illustrative solution study — not a claim of completed client work or achieved results.
Scenario
Each system holds a different version of the customer or order, and information moves through files and manual intervention. A change to one integration can break another, with no reliable way to replay work or locate a stalled message.
- Users
- Product, operations, finance, and technical support teams
- Scope
- APIs, integrations, operational data model, event processing, and observability
- Disciplines
- Domain Modeling · API Design · Backend · Data · Security · Reliability
Solution Architecture
Business Domains
Customer, order, and billing boundaries that contain change.
Events & Jobs
Queues, controlled retry, a dead-letter path, and operations tooling for safe replay.
Security & Insight
Distributed tracing, structured logs, secret management, least privilege, and audit history.
Design & Architecture Decisions
One owner for each concept
The authoritative system for customer, order, and invoice is explicit; other systems consume a defined representation.
Compatibility before purity
An anti-corruption layer protects the new model instead of forcing legacy systems to change at once.
Failure is operable
Every message can be traced and replayed safely, with an alert that explains impact and action.
User Experience
Clear in real conditions
- Actionable errors for technical consumers
- An internal integration status surface
- Documentation with structurally realistic examples
- One correlation ID across services
Engineering
Boundaries built to evolve
- Schema-first TypeScript services
- PostgreSQL consistency and an event outbox
- A queue for repeatable background work
- Rate limits and secret rotation policies
Delivery & Operations
Quality that can be verified
- Contract tests between producers and consumers
- Staged migration with result comparison
- Runbooks for common failures
- SLOs for availability, processing latency, and failure rate
Expected Impact
What should improve when the solution is implemented and operated well?
- More consistent data across systems
- Integrations that can change and test independently
- Shorter diagnosis when a flow stalls
- A staged transition without stopping existing systems
These are target outcomes to validate during discovery and delivery, not published performance figures or guarantees.