[dpark]

> Sit me down and talk about technology for ~thirty minutes.

This is an efficient way to hire a team of good bullshitters. I've interviewed people who did extremely well when we were "talking like professionals" but were unable to do even very simple coding problems.

My bar for coding is really not that high. I don't expect perfect syntax. I don't pick the language. I don't expect "the one answer". I expect people to write code that could work after syntax and small bugs are fixed, and most critically, I expect people to be able to discuss their code meaningfully.

Unfortunately, "ability to write basic code" and "ability to talk like professionals" are not tightly correlated. And I expect both of these things from dev candidates.

[vonmoltke]

I disagree. I have yet to meet anyone who is faking it and cannot be cracked in 5-10 minutes of carefully-directed prodding. In fact, I don't see how it is possible to do extremely well on the "talk like a professional" part and not be able to write basic programs, unless you and I have very different concepts of what "talk like a professional" means.

[dpark]

> I have yet to meet anyone who is faking it and cannot be cracked in 5-10 minutes of carefully-directed prodding.

Coding is a skill largely separate from other critical dev skills, e.g. design. Someone can legitimately have deep knowledge of, e.g., how to build a 3-tier service architecture without actually being able to code. This isn't "faking it". It's a different skill. You can study database partitioning strategies and learn about the latest and greatest frameworks for writing web pages and APIs without ever writing a single line of code. And sure, you can try to probe deeply enough to expose where their knowledge stops, but you're still not probing for coding skill. There's actually a decent chance that you'll end up probing for trivia which is not a very useful filter. "Oh, you don't don't know the auto-generated C++ class members? You clearly haven't actually worked in C++!" Yeah, right. Anything known broadly-enough known that it's reasonable to assume all coders would know it is broadly-enough known that non-coders could learn it, too.

Even if you could probe deeply enough in conversation to expose that they can't code, you could do the same with a few minutes of actual coding. When someone can't code, it becomes clear pretty quickly when you ask them to code.

[vonmoltke]

> Coding is a skill largely separate from other critical dev skills, e.g. design.

I do not believe coding is largely separate from engineering. There are, of course, other skills that are necessary or desirable.

> Someone can legitimately have deep knowledge of, e.g., how to build a 3-tier service architecture without actually being able to code. This isn't "faking it". It's a different skill.

Absolutely. It is also a level of skill I would only expect or look for in a position that was not going to be doing daily coding, such as a systems engineer.

> You can ... learn about the latest and greatest frameworks for writing web pages and APIs without ever writing a single line of code.

Here I disagree. If you have never used a framework or API, you don't know it. I don't care that you can regurgitate the Javadocs; I care that you know things like its pitfalls, quirks, and runtime oddities.

> There's actually a decent chance that you'll end up probing for trivia which is not a very useful filter.

To be clear, I abhor trivia-based interviewing. What I am talking about is practical engineering tradeoffs between one course of action versus another, preferably supported by direct personal experience in the past.

> Even if you could probe deeply enough in conversation to expose that they can't code, you could do the same with a few minutes of actual coding. When someone can't code, it becomes clear pretty quickly when you ask them to code.

Exposing the level of competence a five-minute coding problem can is trivial to do in parallel with a deep engineering discussion. In fact, I think some sort of code should be part of that discussion. I just don't think it should be the "implement this" CLRS problem. It should be something two-way, more representative of what the job is like on a daily basis.

[dpark]

> I do not believe coding is largely separate from engineering.

I could pick up a cookbook and study how to cook a souffle. I could learn enough about this academically that I could answer basically any questions you might ask. Having this academic knowledge is a good thing, but it doesn't mean I've ever even separated an egg. If you really want to know if I can make a souffle, your best bet is to hand me the stuff and ask me to do it.

> Here I disagree. If you have never used a framework or API, you don't know it. I don't care that you can regurgitate the Javadocs; I care that you know things like its pitfalls, quirks, and runtime oddities.

And here I assert that you're either probing on trivia or probing on things that can be learned without using the framework (actually, probably both). The pitfalls, quirks, and oddities are well documented in thousands of blogs.

> To be clear, I abhor trivia-based interviewing. What I am talking about is practical engineering tradeoffs between one course of action versus another, preferably supported by direct personal experience in the past.*

So this is an entirely different thing than pitfalls. Now you're talking about designing systems and dealing with tradeoffs. This isn't coding, and I don't believe you can always discover coding gaps by probing on this.

> Exposing the level of competence a five-minute coding problem can is trivial to do in parallel with a deep engineering discussion. In fact, I think some sort of code should be part of that discussion.

I guess I'm confused about what you're asking in an interview, then. Are your candidates coding or not?

> It should be something two-way, more representative of what the job is like on a daily basis.

I think it's unrealistic to try to get the candidate to solve real-world, day-to-day problems in an hour. This isn't what the job is like. "Design and implement this feature" is not a 45-minute task typically. It's typically days or weeks, so asking a "representative" problem in an interview is infeasible unless you're just doing high-level design, in which case it's not predictive for coding ability.

[vonmoltke]

I think I'm not being clear and may be misunderstanding you.

When I was writing signal processing code, we had four levels of engineering.

- The first was an Algorithm Description Document. This document laid out, in mathematical terms, the algorithms used for various signal processing functions in the system. It was purely conceptual.

- The second was an Algorithm Implentation Document. This document mapped the algorithms to specific parts of the hardware and software system, laying out the logical module structure and data flow. It also specified how the algorithms would be realized in code, since parts of a particular algorithm might need to run in different parts of the system. The AID was still primarily mathematical.

- The third was a series of software design documents. These documents specified the details of module interfaces, code and file layouts, and specifics about what algorithms would be implemented in what functions.

- The fourth was the actual translation of the mathematical algorithms in the AID into actual C code. Most of the engineering at this level dealt with function-level optimization and some platform-specific stuff.

Of those four levels, only the last is what I would consider "coding". It is also the least important. Anyone who can really understand the first three levels and is willing to learn can handle the fourth. As I mentioned previously, there will be differences in efficiency, but not in capability. It would take willful ignorance for this not to be the case. I think this is also what you are considering "coding", but I'm not sure; I also think you might be merging #3 and #4.

Now, most commercial projects do not run this way and, as far as I know, few have dedicated systems engineers to manage the system architecture and APIs. Thus, the software engineers building the system generally perform the work in all four of these levels simultaneously as the system builds out. Despite this, I still only consider the work that fits level 4 to be "coding", and still consider it to be the least important.

What I look for when I interview are engineers who operate very well in levels 1 - 3. If I find that, level 4 is pretty much a given absent the rare pathological case or someone with a very "academic" attitude. The questions I personally ask deal with levels 2 and 3. Those questions cover some of what might be considered coding, like API design and class layout. I do not have candidates actually generate code, though. Some of the other interviewers have candidates write small functions in pseudocode or explain existing, uncommented Java code, though.

I also need to note that we have a take-home test that candidates need to pass before they get an on-site.We have also recently added an open coding challenge which may eventually replace the take-home test. This probably covers your requirement for candidates to code, even though it isn't done in front of one of us.

[dpark]

Yes, I'm generally looking for someone who can do all of those things (though I don't work in DSP, so it's not an exact mapping). I would say that at least part of #3 is coding. If you're actually defining code layout etc., you are basically coding. If you dig deep enough here, you can probably rule out the vast majority of people who can't do #4. I still think it's a more efficient use of time to just ask them to do a bit of coding, though. Then I have certainty on the question rather than an implicit answer.

[brianwawok]

I worked with a team of these before. You can rule our certain types of people with tech questions (i.e. never coded before, only coded hacked, etc.). You cannot rule out

* People who read a lot of blogs so know the lingo, but never code

* People who get the theory but can't actually implement something that works without bugs

* People that over-engineer simple things

[vonmoltke]

> People who read a lot of blogs so know the lingo, but never code

I think this is where my definition of "talk like a professional" may be more strict. I'm interested in understanding, in opinions, in the actual engineering.

> People who get the theory but can't actually implement something that works without bugs

Having spent most of my career working with PhDs trying to design and implement signal processing and NLP algorithms, I have experienced a lot of that. Given the proper attitude, it is fairly easy to correct coding deficiencies if someone really understands what they are supposed to be doing.

> People that over-engineer simple things

The greater offenders are fairly easy to detect in a directed technical discussion. The lesser offenders are fairly easy to correct in code review, again given the proper attitude, as they are unlikely to be doing things that require major refactoring.

In short, I think I place much more emphasis on engineering as opposed to coding. My experience has been that any coding issues people with good engineering skills and an attitude worth hiring have are quickly and easily corrected. You cannot really understand the engineering of a system without being able to code it. You might not be as efficient as someone else, but you are capable.

[dpark]

Also:

* People who have been on a team long enough to learn how things should work but lack the skills to really do the coding.

I phone screened a guy fairly recent who had a very long background (~20 years) in a pretty security-conscious field. He did very well in open-ended design discussions and was able to explain his prior work very well. He couldn't code trivial binary tree operations, though. I can only assume that someone else on his team is carrying most of the coding burden. This guy might be great at a PM-type job (or not, I don't interview for those jobs), but not as a dev.

[vonmoltke]

I feel like there is some detail missing here. What constituted doing "very well" on the open-ended questions? How deep into the engineering did you get? Since you mentioned he "might be great at a PM-type job" it sounds like you didn't go very deep on int.

[dpark]

That one was a phone screen, so no it was not the deepest technical dive ever. But in fairness a 1-hour interview is rarely the deepest technical dive possible. I normally pose some big problem like "design a system that accomplishes X at high scale" and then drill into some area iteratively until we're discussing fairly specific details. At the high level I'm looking for the candidate to recognize tradeoffs between centralized/distributed designs, sanely choose the major components, deal with stateful and stateless components, recognize security tradeoffs, etc. As we drill in we might talk about data partitioning, georeplication, or high availability and implementation tradeoffs there. We might get down to the level of something like handling out-of-order change notifications. Rarely do I drill down to the level of file I/O or memory management strategies.