@german.barros, I don’t think the issue is with toBlocking. In your example, >= 5 threads causes too much parallelization of requests. Couchbase can’t keep up. The lower thread number limits requests sufficiently to avoid timeouts.
I’d have to see the RX Flow example to understand why subscribeOn with the same thread executor has no issues regardless of the thread count. It could be how you’re subscribing.
Jeff