Background check included in processing time applications. In most cases it's not really a distinct part of the process - same people looking at it.
Note, there are security checks - that is distinct. For most likely no more than a records check; for those with some identified security, terrorism concerns, certain Govt ties, would be more involved. From friendly allied countries eg us us Anzac very quick, nato too. Other countries can be more involved or if applicant had military service (for example) or some types of Govt service.
Background check can be completed in a relatively short time while your application is in process.
If your spouse has work history with government organizations or travelled outside their country
for work then you can expect a security check. This can take an extra 9 months or longer.