How do you do SEO for an established e-commerce/high authority site?

I'm applying for an SEO specialist position at an established company with a high authority website. At first sight the website looks flawless and well optimized. It also has a very high domain authority and the like.

• How do you do SEO for these kinds of sites?
• What would be a standardized process for an e-commerce site of these characteristics?
• what would be a standardized process for a norm high authority website?

I ask this because I got rejected from a previous role at a similar position and company.

Thanks