Alexa.com is actually a subsidiary company wholly owned by Amazon. They offer an impressive suite of SEO services to webmasters interested in getting as much 'ranking juice' out of their sites as they can.
On a recent blog post related to the matter the company writes:
"Twenty-five years ago, we founded Alexa Internet. After two decades of helping you find, reach, and convert your digital audience, we've made the difficult decision to retire Alexa.com on May 1, 2022. Thank you for making us your go-to resource for content research, competitive analysis, keyword research, and so much more."
As of now the company has stopped offering new subscriptions but existing customers will still be able to access their accounts and information until May 1, 2022. At that time access will be revoked. Alexa-related APIs will be retired as of December 8, 2022.
Although Alexa.com enjoyed tremendous popularity during the early days of the internet the site has been seeing declining traffic for years and it has reached the point now where traffic is just a fraction of what it once was.
This is the likely reason for sunsetting the service. While it may be possible for Amazon to reinvigorate the service that would be an uphill battle. That is given the popularity of Google's excellent offering and given how deeply entrenched Google is in the market.
If you are an Alexa customer enjoy it while you can. You should begin making plans to transition to something else soon because the clock is ticking. Farewell Alexa.com. As an iconic part of the landscape of the early internet you will be missed.