Ideally it should not take more than 3-4 hours to transfer shares from one Demat Account to another. Transfer of shares Intra depository (NSDL to NSDL or CDSL to CDSL) generally happens immediately on OTP verification. Inter depository transfers take upto 3-5 hours on submission of OTP.
In case you are not able to see the shares you have bought in your DP(zerodha, upstox, angel broking, etc.) You can check the instantaneous reflection of shares in your demat account at the respective depository shares here: