You have a few ways to investigate the Minecraft Realms server status to ensure it is available. There are official outlets you can check out, alongside one that monitors larger servers to show major drops in coverage. The official pages include the official Minecraft Twitter page and the Mojang Support page.
You can check the linked pages regularly to learn about any outages or updates currently happening in Minecraft. If there’s an update or new release for the game, you can expect a few hiccups in Minecraft Realms, and you will want to closely monitor those sources. They should list current problems, that its teams are working on a solution, or provide an answer to a known problem plaguing players.
An alternative website for you to seek out to see any spikes is Downdetector. You won’t receive an in-depth answer or a proper notification about why Minecraft Realms is encountering the issues, but if you will be able to visually see any spikes in the downed activity through a graph. The graph should serve as a good indicator of what’s going on and how widespread it is for everyone playing.
When you notice a spike or a problem in the servers, your best bet is to wait it out and see if things become less of an issue in a few hours. Should there be a more direct solution to the current server issues, the Minecraft teams on Twitter and the Mojang Support page should provide you with more exact steps to solve the problem.