You learned to leverage this knowledge to design solutions optimized for each type of subdomain. We discussed four business logic implementation patterns—transaction script, active record, domain model, and event sourced domain model—and the scenar‐ ios in which each pattern shines. You also saw three architectural patterns that pro‐ vide the required scaffolding for the implementation of business logic: layered architecture, ports & adapters, and CQRS. Figure E-1 summarizes the heuristics for tactical decision-making using these patterns.

Figure E-1. Decision tree summarizing heuristics for tactical decision-making