Changing Domains and SEO

We have two domains, domain a and domain b.

A has been used on an ecommerce site for close to 20 years. the site has several thousand products and sells world wide, uses USD as the currency, has good category navigation, and and a supports sales from two warehouses in one shopping cart.

Domain B is being used on a new website, has just a few hundred products and is using the currency of one country that represents about 1/5th of the sales.

We plan to migrate most of our products to the new website and will over time, add more products and increase reach to other markets.

if we swap domains between the two websites, with this boost the traffic on the new website? In other words, will domain A. if now used with the new site, the one with less content, boost the traffic to that site?

Also, what will happen to the bigger site as a result of changing it’s domain? How long with the search engines take to adjust to the new urls and direct users to its content as before?

Well yes, if you point domain A to domain B, all of domain A’s traffic (after DNS repopulation) will go to domain B. If the URLs for domain A are not mimiced to domain B, or you dont establish a catch-all forwarder, a lot of people who have saved URLs will end up getting 404s.

And then when people do arrive at Domain B, find that it suddenly doesnt have the products or shipping options they were used to having, and they will abandon the site. So… yes, but at what cost.

See above for the first part of this.
The second part… if you just hard cutover the domains, the search engines will take however long it takes them. Noone can give you a “it will happen in X time” answer to this. You can help the search engines by submitting new sitemaps and such, but its still up to the individual search engine’s processing queues and times.

thank you for your answer. Regarding the second part, let me define the question better. It’s not crucial how long it will take the search engines to remap so that they direct traffic to the old content now mapped to a new urls. It it takes a week or two weeks. that doesn’t matter, The question is might the search engine ranks of these pages be harmed in the long run because of this upheaval?

Yes, search engine rankings can be harmed in the long run if the migration isn’t executed with precision. But if done right, Google is fully capable of preserving rankings, even boosting them after domain or URL changes.

It’s depend on how precisely migration happen.