In our almost 10 year-long run in eCommerce we have dealed with quite complex integrations. For these years we have worked with almost any kind of 3rd-party integration to an online store. We are the official developers of all of the courier connectors and of almost all of payment integrations in Bulgaria. One of our most notable projects were with PostNord (shipping, Nordics) & Giropay (payments, Germany).
Meanwhile in the monthly tasks with our clients subscribed for maintenance we have experienced a lot of custom integrations or even custom module development. This skills we have applied in producing of more than 50 modules for eCommerce platforms like Magento, PrestaShop, OpenCart & others.