As dzieciou commented, this can vary pretty dramatically. I will give you some ideas about what I look for when interviewing an experienced QA Engineer. One of the most important things I look for - whether the role is primarily manual or automated testing - is the ability to perform root cause analysis.
For instance, if a candidate has experience working on web sites and web services I would ask them a question such as "If you have a dropdown on a webpage that calls a web service, that in turn queries a database and uses that data to populate the drop down values, then if you click on the drop down and there is no data, how would you try to determine the root cause of the problem?". The things I am looking for when I ask this question would be:
- Their understanding of the architecture
- Do they understand HTTP enough to look at the HTTP response and identify a problem?
- Do they understand Web Servers enough to know where to find log files and what to look for in the log files?
- Do they understand databases enough to find and query the data and find problems?
- Their familiarity with the tools
- Do they know how to use the browser's developer tools?
- Do they know how to log in to a server (Windows or Linux) and find/search the logs?
- Do they know how to use whatever tool to query the database?
- Their logical troubleshooting and problem solving skills
- Where do they start?
- How deep do they go?
- If I modify the problem in some way, how quickly and effectively can they change their approach?
I only look for things that they would be expected to know, for instance, if they worked with windows servers I wouldn't expect them to know how to log in to a linux server with putty and grep the log files, or if they had primarily tested desktop applications I would not expect them to know in depth info about web sites and services, etc.
This gives me some very good data about the candidate:
- It shows a sense of curiosity, it means the person has taken the time to understand the technology that they work on and gone above and beyond simply looking at it from a black box perspective.
- They display some solid logical problem solving skills.
- They will be able to provide more details to developers, and understand when there are separate defects vs one defect with multiple symptoms.
- They will be able to earn the respect of developers
- They will be better able to determine what to test when changes are made.
- They show that they have learned about technologies and tools, which is a good indication that they will be able to learn new technologies and tools.
If it is a role with automation, I would also ask some basic coding questions (or more difficult coding questions if the role is for a senior candidate) as well as some automation specific questions. Some favorites of mine are "Give me 5 ways you could make your automation more maintainable" and "Give me 5 ways you can make your automation more reliable". I am looking for anything either specific to automation like "Use the page object pattern" or specific to writing code in general like using effective logging or commenting, or using various object oriented principles and design patterns. Depending on how senior/junior the candidate is, I would have different expectations for these answers.
Hope this helps.