What Should I Look for in an Ecommerce Solutions Provider?

I’m researching ways to improve an online store and make its ecommerce operations more efficient. I’d like to understand what an ecommerce solutions provider typically offers, including website development, store setup, customization, product management, integrations, and optimization. What factors should businesses consider when selecting a provider, and how can they determine whether the services match their specific ecommerce requirements and long-term business goals?