I've hired many people over the past eight years, had my share of bad matches¹. I evolved my process quite a bit. A core part of what I do today is doing a "Work Trial" with candidates.
The problem with interviews
Interviews are a proxy and give a limited signal to what it's like to work with someone. At best you can tell how experienced and smart someone is, but it doesn't tell you about their work ethic, how hard they work, async communication, are they open to feedback, and if they are a fun person to work with. All of which make a big difference when you're spending significant time with someone every day.
Not to mention that interviews can be gamed, and many candidates optimize for leetcode and answering questions "correctly".
Nothing gives a better representation of what it's like to work with someone than actually working with them.
What is a work trial
Instead of hiring someone after a successful interview, you do a "tentative" hiring decision. You define a period where you two work together, and at any point during the trial period, either party may decide that there isn't a fit and withdraw.
The opposite is also true, either party can let the other know early in the process if they think that there's a good fit.
Work trials are paid. We pay the candidate in full if they decide to withdraw.
Duration and arrangement
This changes on a case-by-case basis. You should aim to be flexible and fit the candidate's schedule.
Ideally you get 2 to 4 weeks of full-time work together. This works well for people in between jobs and students. For candidates with a full-time commitment, you can do a 2-3 day project or work part-time² for two weeks.
Pros and cons
Upsides:
- Stronger interview signal
- Hedges against poor matches, reduces the chance of "firing" new hires
- Candidates get a better understanding of the work and culture, lowers the chance of them leaving shortly after joining
Downsides:
- Top candidates are often busy and don't have time to put aside days for a potential company³
- More time consuming than the typical interview loop
¹ There are no bad hires, just bad fits. I've seen people perform poorly in a position just to move and do incredibly well in another.
² The challenge with part-time is that if the candidate underperforms, it's unclear if it's due to not putting in enough hours, or their ability.
³ You emphasize that the work trial is important for the candidate, to determine if the company is a good fit for them.