Doing Without Databases in the 21st Century (2018)

He kind of glosses over any kind of concurrency issues with "The operation on the access service is done in a single-threaded manner. Only one person in the room at a time. This won’t work if the operations are lengthy as it stalls every waiting operation. But in this case the operations are very lightweight so you can get away with it."

If you have a problem that is a. small enough to fit into 256GB of memory, b. does no operations that would introduce undesirable latency, and c. does not need to scale locks to handle millions of concurrent access, then go for it.