Question: I'm looking for a platform that provides guaranteed solutions for web and app development, including REST API development and e-commerce solutions.

If you want a broad platform for web and app development, Topcoder is a good option. Topcoder is a marketplace that lets companies tap into a global pool of software developers, designers, data scientists, AI practitioners and QA engineers. It can handle a variety of tasks, including REST API development, e-commerce, AI, data science, web and app development and quality assurance. With an integrated AI assistant to help define and refine project requirements, and pricing that varies depending on project scope, Topcoder promises high quality results and a high customer satisfaction rate.

Another good option is Amplication, an open-source .NET and Node.js app development platform that uses AI generation to create production-ready backends in a matter of minutes. Amplication features include full-featured GraphQL and REST APIs, role-based access control, microservices support and continuous Git sync. It also comes with an automatically generated React Admin UI, which makes it suitable for everything from single services to large-scale microservices architecture.

For a low-code approach, Backendless is a collection of tools for building and running high-performance apps as efficiently as possible. It includes a visual UI builder, codeless logic for frontend logic and direct API integration for easy data management. The platform supports responsive apps for web and mobile, real-time database capabilities and integration with third-party services like FlutterFlow and Zapier. Backendless offers flexible deployment options and a variety of pricing plans, including a free option.

Last, Supabase is an open-source Firebase alternative that lets developers build production-ready apps with a Postgres database, user authentication, instant APIs, real-time subscriptions and storage. It supports frameworks like Next.js, Svelte and Flutter, and offers features like edge functions, vector embeddings and a built-in data management dashboard. Supabase offers a free tier with unlimited API requests and several paid options, making it a good option for developers who want a flexible and affordable option.