Instruction file imported from AlbertoBasaloAcademy/Redinet-Copilot_Net (.github/instructions/lib_inmemory-repositories.instructions.md). Copyright stays with the author.

In-memory persistence

Persistence is in-memory by default to keep local execution deterministic and dependency-free.

Thread safety

• Treat repositories as shared state; make them thread-safe.
• Prefer ConcurrentDictionary<TKey,TValue> for keyed storage.
• Avoid returning mutable references that callers can modify.

Deterministic behavior

• Prefer deterministic IDs (for workshop/test repeatability).
  • Example approach: long IDs using Interlocked.Increment.
• Ensure repository operations have deterministic outcomes for the same input.

API design

• Repository interfaces should be small and feature-focused.
• Prefer methods that express intent:
  • TryCreate(...) returning success/conflict
  • GetById(...) returning nullable

Conflict handling

• Use atomic operations (TryAdd, TryUpdate, TryRemove) where possible.
• Map persistence conflicts to Business outcomes (and then to HTTP 409).

Data boundaries

• Keep repositories in lib/Persistence.
• Keep domain models in lib/Models and DTOs in lib/Dtos.
• Persistence should not depend on Presentation.