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The client wants to close the current e-commerce website and open a new one on a completely different engine without losing income. I have no idea how to approach this topic. Old site has over 100 000 pages, and in terms of SEO is quite great - we hit almost every important keyword in our niche but thanks to heavy modifications of source code site become unmaintainable. Content on new shop will be almost 1:1 with old page but: domain will be different (I can't explain to the client that this will damage our core brand). Beacuse of that I'm forcing idea of going with brandname.com/shop domain instead of newshop.com beacuse our main brand is well known to our customers, not as much as old shop but still better than new shop brand. engine and design will be different we will lost almost 30 000 backlinks. budget: only IT. No content and seo tools budget. BONUS: client hired before me some "SEO magician" - now SEO audit score with tools like ahrefs etc. is around 6 - 12% for 100 000 pages on new shop. Great. Does anyone have idea how to approach such task with minimal losses?