You need to keep below points in mind while preparing for an interview as a Senior Software engineer:
As a senior software engineer you will be interviewed for specific skills like Database administrator, Application programmer, Systems engineer, ERP specialist, e-comm specialist, etc. There are further bifurcations in skills of an application programmer like Python, PHP , ROR, Java, iOS, Android, Node js, etc and these can be divided further on the basis of frameworks like spring , Django, eCommerce platforms like Hybris, WCS, Sales Force, etc . As a senior software engineer you are going in as an experienced candidate and the interview would always be around your previous experience.
So you need to master your skills whatever you are being interviewed upon. Generally there are two technical rounds mostly dealing with your skills but also the surrounding areas (eg: Spring developers can be asked core & advanced JAVA concepts).
Mind it you can always be asked questions on Data structures, Algorithms & Database design on any interview for an application programmer. So one needs to have a comprehensive idea about these topics on their tips.
If you are changing your domain (eg: from JAVA to Node js developer) you still need to answer questions about the new skill like an experienced candidate in that domain. At least you need to have a fair idea about the new skill set to get a job as a senior engineer, else you would be considered as a fresher(entry level) programmer in that skill.
After the two technical rounds of interview, there will be a HR round. This is majorly to discuss you compensation expectations and preferred location.
Generally everything moves in a timely manner but don’t lose patience & hope if you don’t receive calls in a couple of weeks. A delay is also expected as Accenture is a very large organization. If you have cleared rounds you will surely receive calls.