Immigration, Refugees and Citizenship Canada (IRCC) reviews Express Entry applicants every 2-4 weeks. Hence, if you receive a high score, it is possible that you will receive your ITA within just a few weeks. Your profile will remain active in the Express Entry pool for 12 months so even if you do not receive the ITA after the first draw, you might receive it at a later date.
If you are not selected within one year, you can submit a new application and try again.