Lenovo has not gone with the tried and tested Snapdragon 615 SoC for the Vibe X3 considering its pricing. It has gone a notch higher and got the Qualcomm Snapdragon 808 chipset which houses a hexa-core processor which one dual core cluster clocked at 1.8GHz and one quad-core cluster clocked at 1.2GHz.
This is paired with 3GB of RAM. While handling the phone for the limited time, we did not notice any lag or stutter, but we will need to test the phone in the real-world scenario to get a complete picture