Prioritize throughput capacity, pick-and-pack accuracy, inventory accuracy, and peak-season scalability. Verify carrier connectivity (parcel, LTL, rail), returns and reverse-logistics processes, and the 3PL’s WMS/API integration readiness. Also assess labor stability, real-estate cost structure, and clear SLA and chargeback terms.

Closer proximity to interstates and parcel/LTL hubs reduces transit zones and carrier miles, lowering freight spend and transit variability. Warehouse infrastructure—cross-dock capacity, number of loading docks, and handling equipment—impacts dwell time and handling costs; automation and volumetric efficiency reduce per-unit fulfillment cost.

Negotiate OTIF and on-time pick-and-ship targets, order accuracy percentage, inventory accuracy, average order cycle time, and max daily throughput. Include penalties or remediation for SLA misses, defined chargeback processes, and scheduled performance reviews tied to seasonal forecasts.

Request WMS documentation, API/EDI specs, and examples of live integrations with marketplaces or ERPs. Validate uptime, disaster recovery, and cybersecurity controls. Review audited performance reports, client references, site visits (or virtual tours), and pilot programs to test order flows and inventory accuracy before committing.