Prioritize warehouses with scalable racking, dedicated cross-dock lanes, sufficient yard space for trailer staging, and proven WMS integrations for inventory visibility. Also confirm loading dock density, security, and temperature control if you handle mixed SKUs.

Carrier access directly affects transit times and cost. Evaluate the 3PL's parcel and LTL carrier partnerships, average days-in-transit to your primary delivery zones, and ability to route via multiple carriers to optimize cost and SLA. Consider seasonal capacity commitments.

Compare: inbound receiving and putaway fees, pick-and-pack rates, storage (per-pallet and long-term), outbound carrier passthroughs, replenishment and returns handling, and any minimum monthly charges. Factor inventory holding days and shrink assumptions.

Look for a WMS with API connectivity to eCommerce platforms, order management that supports split shipments and inventory allocation, real-time reporting, EDI or API for carrier manifests, and support for barcode/RFID for cycle counts.

Review the provider's peak staffing plans, temporary storage options, cross-docking capacity, contingency carrier agreements, and historical performance during peaks. Ask for a capacity escalation plan and KPIs for order accuracy and throughput.