The way I like to approach CVs/cover letters is, assume that you’ve got the role, that you’ll nail the role, and your job is to let the employer know why you’d be a great and easy fit. YMMV though. Even with the best CV and cover letter I think it’s still a coin flip!

Cover letters

I love cover letters that are personal and easy reading.

You shouldn’t sell yourself short, or give them reasons to not hire you. Instead, you can keep sections about how you want growth and learning :)

When talking about what interests you about the company - why? What is it about the type of work you’d expect that interests you? What would you expect to learn?

CVs

If I was looking for a senior developer I’d be looking for:

At most three pages, 2 is best
There’s something about it that catches my eye and is memorable
The CV is tailored to the role
A range of experience in different kinds of companies
Volunteering and other experiences, to show they care about teaching others
An attention to detail in the CV
Not just talking about technologies