Interviewing someone is hard. In fact, I'm not sure many of us really know how to do it well. Looking at the past hires in most companies I've known, I find that all too often the success of hires in developing software is a bit of a hit and miss effort. Some hires do well, and some don't quite perform as expected. Why is that? Wouldn't you expect that we could adequately test someone's skills as a developer? After all, we know what kinds of code we expect people to write. Shouldn't there be some sort of test that you could have someone complete, even across a few hours, that would allow them to show what they can produce?

I ran across an interesting post from Ore Eini that looks at a way of interviewing people by asking them to improve code. Rather than a take home test, or having someone develop code from scratch, Ore gives them a file and some code, then asks them to make it faster. The interviewee has around an hour (mentioned in the comments), but this is a test of whether or not someone understands how to read and write code well.

Perhaps there's a good way to do this in the SQL world as well. Can we take a loop or a complex join and have a user rewrite a query to be more efficient? Some of the changes in T-SQL in recent versions (especially 2012) can dramatically change the way you write code. Perhaps a candidate should be tested to see if they actually know how to avoid Grant's seven sins? I bet more than a few people would want to know if candidates would remove, or at least question, the use of NOLOCK.

There are many reasons why a candidate might interview well and then not perform as expected on a day to day basis. Life changes, we have outside distractions that might affect us at work. During the workday, we may struggle to get along with co-workers. Our managers might not bring out the best, or even the good, in us. Perhaps we are asked to perform tasks that weren't covered in an interview and are outside our area of expertise. Perhaps we just don't try as hard after we've achieved our goal of getting he job.

There isn't going to be any magic, guaranteed way of ensuring we hire people that will always perform up to their abilities. That doesn't mean we should give up. I would really like to see us continue to try new techniques, share ideas, and most of all, continue to inspire and motivate others to learn more about their craft and constantly improve their skills.

By the way, if you're interested in the code side of things, Ore discusses some basic improvements and then more efficiency changes. One interesting thing, moving away from Linq dramatically lowered the memory allocations and working set size. Is this a big deal? It really depends on the way in which your application is structured, but this is an optimization that might be worth doing early and often with a little developer training on how to better write queries.