Software Architecture Patterns, Antipatterns, and Pitfalls

Chapter 12. Key-Based Event Contract Pattern

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When triggering events or sending messages, architects are faced with a decision about the event payload. They can choose to create a payload contract containing all the data necessary for reacting and responding to the event (that’s the Data-Based Event Payload contract in Chapter 8), or they can choose to send only the keys of that data. When responding to the event, services must retrieve the data from a database (that’s this pattern). This chapter focuses on the trade-offs and implications of the Key-Based Event Contract pattern.

Table 12-1 summarizes the metadata for the Key-Based Event Contract pattern.

Table 12-1. Metadata for the Key-Based Event Contract pattern

CATEGORY	METADATA
CONTEXT:	Contracts, Event-Driven Architecture, Message-Based Architectures, Microservices
IMPROVED:	Bandwidth Usage, Data Consistency, Data Integrity
DEGRADED:	Adaptability, Elasticity, Evolvability, Responsiveness, Scalability, Throughput

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