Prioritize WMS/API integration, SLA guarantees for pick/pack and shipping, inventory accuracy, returns processing, and demonstrated throughput for your peak volumes. Also evaluate racking and temperature control options, carrier connectivity to national lanes, and the 3PL’s reporting and audit capabilities.

Location drives last‑mile miles and carrier rate bands: sites nearer trunk highways and feeder routes reduce transit time and access more carrier lanes. Consider proximity to consolidation points, regional ports, and intermodal links; these factors influence fuel surcharges, inbound consolidation costs, and delivery promises.

Negotiate clear SLAs for order cycle time, inventory accuracy, and on‑time shipments; define chargeback rules, minimums, surge pricing, audit rights, and termination notice. Include regular KPI reporting, penalties for missed SLAs, and mechanisms for capacity ramping during peaks.

Look for documented peak‑season playbooks, established temp staffing lines, flexible or overflow warehouse options, cross‑dock capability, and tested carrier surge plans. Confirm past performance data for peak periods and whether the 3PL uses elastic WMS features to manage SKU and order spikes.