@Oksana It means less than 1 hour per year, on average, under specific SLA rules. If you want, tell me what you’re hosting (website, SaaS, game server, API), and I’ll tell you how much uptime you realistically need and how to design for it.
Microsoft databases and "mission critical" can never be used together. Either your workload is important, or you can run it on this crap. But by deploying SQL Server, you are defining your workload as "not worth thinking about." Because clearly, it wasn't thought about.