It seems likely to me that a recession or pandemic affects more than just the OP's business, so while that one customer is probably meaningless to AWS, the thought process that led to scaling back spending could be meaningful.
0.3% of monthly revenue from a single customer's reduced spending only a couple months in to a multi-year recession is pretty alarming.
Makes me wonder if OP's company is particularly exposed to retail, travel, or another sector severely impacted by the first order effects of the virus.
That sounds like a lot to me for just one customer. But in the absence of much more data about AWS customers and revenue, it's hard to draw any meaningful conclusions.