How to ramp up a slow learner?

First, I recommend my deep-dive on how I was able to grow mentees extremely quickly at Meta. I'm also going to assume that you're an engineer mentoring another engineer.

From there, my advice is split up into 2 broad categories, which I'll separate into 2 different comments.

1. Teach them systems
2. Improve with a laser focus

Teach Them Systems

• Your goal is to teach them how to fish, not just give them fish (as this operating model will keep them dependent). Whenever you give this person help, make sure to explain the thought process you used to arrive at your answer.
• Here's an example: Your mentee gets a task and is unsure where in the codebase to start and make the changes. You give them the classes they need to modify to get started. On top of that, you should also tell them the thought process and tools you used to find those files. This can be something like, "This task requires changing the checkout button to a different color, so I did a grep for "checkout" in our codebase to get some collection of classes. From there, I added print statements to the relevant files, ran the code to the relevant point, and saw which print statements fired to identify which code matters."
• Over time, they should be learning these systems, and you should be more and more hands-off to "wean" them off of your hand-holding. Let's say you have taught them the system to find relevant code. If they ask you again to do this for them, respond with a question: "So we know this task deals with this feature - What's the first step we can try to identify clusters of potentially relevant code?" It's possible they aren't independent yet as you're too nice and keep helping them super directly.
• Tell your mentee about this mentality as well. It shouldn't always be up to you to proactively churn out an encyclopedia of knowledge with every interaction. Tell them that it's also up to them to ask follow-up questions when they receive help and don't fully understand the answer.
• I also recommend this discussion around how to answer questions effectively.

Improve With A Laser Focus

• Humans are naturally terrible at multi-tasking, and this will be even more true with stressed out low-performers.
• As a mentor, you should prioritize all the areas this person needs to improve in and stack rank them accordingly. From there, go through the list one at a time, spending 2-4 weeks on each one. After you see clear improvement in an area (which you should after so many weeks), you move on to the next one.
  • If they're an engineer, the first area will probably be "Writing code independently". So let's say you tackle that first - After their coding velocity and independence goes up, you can focus on the next area (e.g. "Participate more in meetings").
• I recommend getting input from others (manager, tech lead, etc) on what this prioritized list of improvement areas should look like.

Some other thoughts:

• Maybe this person just needs a break - Stress is a common culprit behind low performance. If you feel like they're stressed out, the solution could be a 2 week break for them or something.
• Meet up a lot - If you're not meeting at least once a week, do that. You might even want to crank this up to twice a week. I also recommend pair programming to get additional face-time.

Lastly, an unfortunate truth is that many low-performers can't be saved. Some might not even deserve to be saved (a lot of low-performers are just jerks and hard to work with). If you feel like you aren't seeing results even after applying all this advice, you should have an honest discussion with your manager about the future of this mentee within your team.

At the end of the day, you need to make sure the team succeeds. Low performers can take others down with them if they suck up too much of your time. Check out this other discussion on evaluating whether you should invest into a struggling teammate.

I once had a mentee (intern) who was an amazing C coder but had trouble with "dev ergonomics" things like UNIX utilities. I tried to help her with the non-core-C tasks so she could maximize her time doing C coding. As Alex said, I would teach her a mental operating model for the non-C tasks and she did become more proficient by the end of her internship. I recognize your situation may be a little different.