What happened is a scheduled maintenance that had to be done. If not, the site was at risk of eventually crashing in the long run.
Even though the site is free for now, nothing is entirely free. The time/space on the server allocated to us was almost used up. To save costs, this maintenance had to be done.
As we scale the platform in the long run, we might have to move from being completely free to offering paid features to handle growing needs and demands.
Hopefully we have smooth running from now henceforth.