Question: I need a platform that supports online classes with large concurrency and offers engagement tools to motivate learners.

If you're looking for a platform that supports online classes with high concurrency and engagement tools, CodeTantra could be a good option. It offers secure online classes with features like 2-factor authentication, role-based access control and live polls. The platform also comes with virtual classroom tools like real-time annotations and break-out rooms, so it's a good option for online learning and teaching.

Another good option is Top Hat, which uses interactive courseware to engage students and gives instructors tools to personalize learning. It offers interactive response tools, customizable textbooks and real-time data insights. Top Hat's tools are designed to keep students on track and encourage them to participate with interactive assignments, quizzes and discussions.

If you're looking for a more general-purpose suite of tools, check out Instructure and its flagship product Canvas LMS. Canvas handles course material, communication, assessment and video learning. It also offers related tools like Canvas Catalog for course registration, Canvas Credentials for digital badges and Canvas Mastery for assessment tools, so it's a good option for K-12, higher education and professional education.

Last, Lens is an interactive learning platform designed to increase engagement with real-time polls, quizzes and Q&As. It offers gamification tools like leaderboards to track and encourage student participation, along with real-time engagement data and post-session dashboards to measure session success. It's good for institutions of any size looking to increase learner engagement and interactivity in live sessions.