Non-blocking secondary reads are now available in MongoDB 4.0, allowing users to scale-out read throughput and reduce network latency by reading from the nearest replica set member without blocking other readers.` `This improvement ensures consistent data views across the primary and secondary replicas, guaranteeing predictable low read latencies and increased throughput for users.` `The change is made possible by using storage engine timestamps and snapshots, which enable queries to read from a snapshot of data while replication batches are applied simultaneously to the secondary.