What’s the best approach to design a scalable and reliable real-time chat application for sending messages, creating groups, and other updates [closed]

I am planning to create a chat application. I want to get some clarification on this.

which one should I use:

1. Using REST APIs for operations like sending messages, creating groups, and updates (to ensure data consistency), while using WebSocket for broadcasting real-time updates to users.

2. Using WebSocket for both sending data and broadcasting updates, skipping REST entirely

Key considerations:

• Scalability for enterprise-level applications.
• Data consistency and transactional integrity.
• Real-time performance with low latency.
• Ease of debugging and maintaining the codebase.

What’s the industry-standard approach for chat systems like WhatsApp, Slack, or Microsoft Teams?

I got two suggesstion. Which one should I select. And why?