Distributed Systems, Event-Driven, and SaaS Patterns
What This Chapter Is About
Teach distributed architecture as a set of explicit commitments about boundaries, coordination, ownership, isolation, and failure.
Keep one durable idea in view:
Distribution creates independent boundaries only when ownership, contracts, and failure behavior are designed together.
Sections
How the Chapter Develops
The chapter develops in this order:
Explain what distribution adds beyond putting components on separate runtimes.
Establish service, data, team, and tenant boundaries.
Choose coordination contracts deliberately.
Design for duplicate work, partial failure, contract change, and recovery.
Apply the model to SaaS isolation, fairness, visibility, and economics.
Test the complete model in a multi-tenant order-platform scenario.
Together, these sections show that distributed, event-driven, and SaaS patterns are different views of boundary design under change and failure.
What You Will Be Able to Do
By the end of this chapter, the reader should be able to:
Challenge weak service boundaries and identify hidden coupling.
Choose between request-response, messaging, events, and workflows.
Explain how idempotency, versioning, replay, and observability support recovery.
Select tenant isolation approaches from risk and business requirements.
Key Ideas
Network separation alone does not create a useful service boundary.
Asynchronous communication changes coupling; it does not remove it.
Data ownership and contract evolution determine whether teams can change independently.
SaaS design joins security isolation, noisy-neighbor control, operations, and unit economics.