Create a super large food website for data interaction

As a large food website data interaction, the company now wants to build a large food website. System Regulation includes businesses, coupons, mobile phones, membership cards, etc. for database design, interfaces, servers, programs, and other things that need to be paid attention to, for the first time, such a large project is a bit inaccurate. There is a large volume of merchant data and a large volume of traffic. I hope to have some experience in this area to create a large food website for data interaction
Now the company wants to build a large food website.
System Regulation includes Merchants, coupons, mobile terminals, membership cards, etc.
What should I pay attention to when designing databases, interfaces, servers, and programs?

The first time I met such a large project, I was a little confused. There is a large volume of merchant data and a large volume of traffic. Hope that experts who have experience in this area can give some suggestions.
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1. Database read/write splitting
2. static content CDN
3. load balancing with NGINX
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Since the project is relatively large, we should finish it first and then consider optimization.
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We need to find the bottleneck first, and then solve it one by one.