Comprehensive and Detailed Explanation From Exact Extract:

Pega’s design patterns for limited availability and concurrency, as taught in Pega Academy’sApplication Design Missionand thePega Certified Lead System Architect Study Guide, leverage Pega’s built-in locking mechanisms to manage resource contention efficiently. Locking is the standard approach for ensuring concurrency control in scenarios like booking limited seats.

Option A (Correct): Using instance locking (e.g., optimistic or pessimistic locking) on data or case instances is the best approach. Pega Platform automatically manages concurrency by ensuring only one user or process can modify a locked instance, preventing conflicts. This is a core feature, as documented in theLocking Mechanismssection of Pega Community.

Option B (Incorrect): Using data instances with flags to manage locks and availability is overly complex and error-prone. Pega’s native locking mechanisms are more robust and eliminate the need for custom flag-based logic, per theConcurrency Designmodule.

Option C (Incorrect): While case instances can use locking, creating a case for each request is unnecessary unless the request requires a full case lifecycle. For simple resource allocation, data instance locking is sufficient, as noted in theCase Designguidelines.

Option D (Incorrect): Circumstancing the rule resolution algorithm does not address concurrency or availability. Circumstancing is for rule specialization, not resource management, per theRule Resolutionmodule.