The following test code hangs on the CRUD upsert operation even when maxTimeMs was used: const dbName = "test" ; const collName = "write_conflicts_with_non_txns" ; const testDB = db.getSiblingDB(dbName); const testColl = testDB[collName]; const sessionOptions = { causalConsistency: false }; const session = db.getMongo().startSession(sessionOptions); const sessionDb = session.getDatabase(dbName); const sessionColl = sessionDb[collName]; // Clean up and create test collection. testDB.runCommand({drop: collName, writeConcern: {w: "majority" }}); assert.commandWorked(testDB.runCommand({create: collName, writeConcern: {w: "majority" }})); const txnOp = { update: collName, updates: [{q: {_id: 1}, u: {$set: {t1: 1}}, upsert: true }] }; const nonTxnOp = { update: collName, updates: [{q: {_id: 1}, u: {$set: {t2: 1}}, upsert: true }], maxTimeMS: 100, }; session.startTransaction(); assert.commandWorked(sessionColl.runCommand(txnOp)); assert.commandFailedWithCode(testColl.runCommand(nonTxnOp), ErrorCodes.MaxTimeMSExpired) // It hangs here