I'm a first time tech lead (CTO, but functionally more of a tech lead) at a start up and I've been struggling with the advice of "holding someone accountable".

My vision for culture was to use a KanBan process so that we could quickly iterate, be agile, and set up a sustainable workload. Mostly using Eric Brechner's "is this task less than 5 days?" to break work down and put it on the board.

So far this has worked out well for 3 developers on the team -- they work hard, communicate often, and really try to push the ball down the field every day. Code is checked in on a daily / every other day basis and overall have a high degree of "accountability" to work hard every day.

We brought on a senior backend developer in May who had previously worked at a bank for 10 years. He was meant to be a key hire to take over on some of my involvement with the backend codebase (note that I am not the original author, it was originally written by a previous contracting house). Overall I would describe him as "okay" -- has been slow on his tasks ("is this less than 5 days" = 5 days), overshooting timelines that he gives (everything is always "1 or 2 days away") , and "okay" quality.

- I'm a developer and understand that there is an element of "it takes as long as it takes", but I want to start thinking in days instead of weeks for tasks

- I had a 1-on-1 with him today and he describe it as "relaxed" which is definitely not how I've been feeling

I'm not quite sure what to do in this situation -- clearly there is an element of mismanagement on my end, but there is also an element of "this person is not driven like the rest of the team" that I don't quite know how to handle. How do you determine how much is your own failure as a manager, versus how much is someone just "not working out"?

- Do I just need to get really specific about asking "how long will this take" for every task and then trying to hold his feet to the fire when we get there? What does this look like?

    - "You said 2 days ago that it would be done in 1-2 days, what's going on?" What if they come up with excuses?

    - I have an agreeable personality which I am trying to overcome, and so am trying to figure out how to navigate conflict in a healthy way

Any help / resource recommendations would be greatly appreciated!