Preparation advice for SDE-3 and above roles

Just to be clear, does SDE-3 refer to Senior Engineer? The terminology varies for different companies (see promotions.fyi for examples).

For senior roles in Big Tech, there will still be a substantial portion of the interview focused on DSA, but you'll also likely get asked about system design. So you should come prepared to talk about the interesting tradeoffs when designing a sample application, along with some good stories about your experience building sophisticated systems.

Here's the Taro guide on prepping for DSA interviews and system design. I'd also recommend going through the system design playlist where Alex walks through the details of an actual Taro feature.

Finally, check out some of the discounts available in Taro Perks which give you discounts to services like Neetcode and Formation.

How much should I focus on DSA, system design, machine coding etc?

This will depend a lot on the company. Figure out what your upcoming interviews will have (to the highest accuracy you can), and adapt your interview prep regimen accordingly. Here's our guide on how to do that: "How to figure out what's going to be on an interview?"

For senior+ interviews, the signal on behavioral and system design are especially important, so I recommend reading through this as well: "Quality to demonstrate for staff MLE during interview?"

Lastly, here's our playlist on effective interview prep: [Taro Top 10] Effective Interview Prep