Last Christmas, the Nintendo eShop had an overload downtime accident, and this Christmas, considering that many players will be buying new Switch, games, and gift cards, Nintendo warned in advance that the server might be unstable.
On the Nintendo Japan customer service account, the company warned that access to the service will occur centrally, and some gamers may not be able to create a Nintendo account smoothly; if players have plans to use the new Switch on Christmas weekend, then they can try to register a Nintendo account in advance. The content only mentions account-created content, but if eShop crashes like it did last year, players won't be able to buy or download the game.
Creating a Nintendo account can be done not only on the Switch, but also on the Nintendo official website, and it does not require players to hold the Switch.
Nintendo sold millions of Switch on Thanksgiving last month, and these new consoles could generate a lot of demand for games during the Christmas season, most likely overloading Nintendo's servers, so if you have a need to sign up for an account or buy games during the Christmas period, you can be prepared ahead.