Function coalescing_memory_stack 

pub fn coalescing_memory_stack() -> MetricsBlockStore<CoalescingBlockStore<MemoryBlockStore>>

Create a high-performance write-coalescing stack for in-memory operations

Combines:

• In-memory storage (no persistence)
• Write coalescing for batching (1000 writes per batch)
• 100ms flush interval
• Metrics tracking

Best for: Temporary high-throughput write workloads