Accessory dwelling units (ADU) or granny flats as they were previously called offer one way to increase housing stock in already developed neighborhoods. Check out this google doc and article on the trends between 2012-2019. It looks like Orange County (the county itself) saw a huge jump in ADU permits in 2019. What does your city look like? (Click on the yellow cell and a drop down menu of city and county names appear–the graph updates based on the jurisdiction selected.)