Разработка клиентов API с использованием PHP, RoR, Grape, MySQL, Postgresql. API: - Google, Yandex, - RbkMoney, Yandex. Kassa, PayPal, CloudPayments, ... - Nets E-Com, Paysera, SEPA (Nordia, Danske Bank), ... - Merlion, Marvel, OCS, Elko Ecommerce, ...