Multi-tenant event fan-out

Design a multi-tenant customer-data-platform ingestion pipeline that receives event streams from thousands of customers (each a business) and routes/transforms/forwards each customer's events to that customer's chosen destinations (their warehouse, ad platforms, email tools), fan-out of one event to up to 30 destinations. Per-customer volumes vary wildly (a few/sec to 50k/sec). One slow or failing destination for one customer must not back up or drop other customers' or other destinations' deliveries. Design ingestion, fan-out, and per-tenant/per-destination isolation.