Version 3.3.0 of the Node driver appears to have a regression where readPreference is not adhered to.

Specifying readPreference=secondary in the connection string with version 3.2.7 results in the find() operation being executed on a secondary node, however the same code with 3.3.0 sees the operation executed on the PRIMARY node.

Connection string and options:

var url = "mongodb://JM-METABOX:27001,JM-METABOX:27002,JM-METABOX:27003/?replicaSet=rs&readPreference=secondary";
const client = new MongoClient(url, { useUnifiedTopology: true, useNewUrlParser: true, monitorCommands: true });