[JamesBarney]

I've seen huge differences in productivity between people who've been working with a given stack with for years vs months.

The quality just isn't even close. Recently I outsourced a project to two groups of people. A jr dev who had 2 years of experience but all of that experience was with the tech stack, and 2 sr devs (10 yrs experience) who had < 6 months experience with the tech stack. And the jr dev (who was an inferior dev in general) blew them out of the water because of the tech stack experience.

And honestly in terms of raw talent I think the sr devs were better, but it just didn't make up for the lack of tech stack experience.

[jghn]

What sort of time are we talking about on these projects? If you're looking at something that has to be done in a few weeks, sure. In a normal role where I expect the person to stick around for a couple of years I'll take the person with better overall skills every day.

[JamesBarney]

On the order of 4-8 weeks.

Original poster used the term fluent for someone with a few weeks to months of experience which both Sr devs had.

[fonix]

In your example it the answer may be “none”, but I’d be curious of the amount of tech debt that may have been introduced by the jr vs the sr’s; whether or not sr’s had better intuition.

[JamesBarney]

Jr introduced far less tech debt because they knew the patterns and best practices around the tech stack where as the Sr developers didn't.

So the Sr devs wrote a bunch of really funky react code and the jr dev just wrote normal looking react code.