Zoho Sheet was painfully slow for around 6 hours from Sunday 8:30 pm PST to Monday 2:30 am PST. We apologize for the slow response time. This happened basically due to a huge number of requests (hundreds of thousands) to couple of public spreadsheets which were linked to from a popular website. We restored the site to normalcy by redirecting public spreadsheet views to a different part of the infrastructure there by reducing load on our servers serving regular users.
We hadn't anticipated that a spreadsheet (we are not talking about a popular video here!) would get hundreds of thousands of views in a matter of a few hours. We are working to speed up and avoid such performance bottlenecks when public spreadsheets become very popular. It is not a difficult problem to solve (caching), just one we didn't anticipate.
Again, we apologize for the intermittent issues and slow response times in Zoho Sheet last night. Until we put in a permanent solution (about 2 weeks), please contact us at support to let us know if you expect your spreadsheet or document is going to get a lot of page views, so we can plan ahead and redirect the traffic accordingly.