Metrics Ingestion

Design a multi-tenant metrics service. Producers send batches, clocks may be skewed and a single label can create millions of series. Queries need recent aggregates and explicit retention.

• Authenticate tenants and validate bounded metric batches.
• Acknowledge only after durable append.
• Handle retries, late samples and replay under a stated duplicate policy.
• Enforce cardinality quotas and retention before resource exhaustion.