Question: I'm looking for a scalable API to build a social network with real-time activity feeds and chat functionality.

If you're looking for a scalable API to build a social network with real-time activity feeds and chat, Stream is a great option. It offers a comprehensive suite of APIs including an Activity Feeds API for real-time updates, a Chat Messaging API with offline support, and a Video & Audio API with strong security measures. The platform also provides UI kits and tutorials to help with integration and customization, along with flexible pricing plans to suit different needs.

Another solid choice is Ably, a real-time digital experience platform that supports live chat, data broadcasting, data synchronization, and multiplayer collaboration. It offers a free tier with 6 million monthly messages and 200 peak concurrent channels, and also supports multiple client and server libraries. Ably ensures high reliability with a 99.999% uptime SLA and strong data integrity, making it suitable for large-scale real-time applications.

For a more feature-rich platform, consider PubNub. It allows for immersive real-time experiences through chat, push notifications, and location sharing. PubNub handles massive traffic volumes and supports end-to-end encryption and fine-grained authorization. It also offers tools for real-time decisioning and AI integration, making it a versatile choice for various use cases including social networks.

Lastly, Tencent RTC is another strong contender, offering APIs and SDKs for video calls, voice calls, chat, and conferencing. It supports multiple platforms and emphasizes high availability and low latency. With a pay-as-you-go model and discounts for startups, Tencent RTC is a scalable option for developers looking to enhance their social networking applications with robust real-time communication features.