The first 90 days in a new leadership role are simultaneously the most important and the most disorienting period of your tenure. Everything feels urgent. Everyone has opinions about what you should focus on. And the temptation to prove yourself by making immediate changes is almost irresistible.

Having started new leadership roles at both start-ups and large corporates, I can tell you that the single most valuable thing you can do in those first 90 days is slow down. Not because urgency isn’t real, but because acting on incomplete understanding almost always creates more problems than it solves.

Understanding Before Action

Will Larson is blunt about this: rushing to make changes before understanding the problem’s shape is the most common mistake new engineering executives make. The two other frequent traps are judging without context, “this technology is terrible, what sort of fools made this decision?”, and reminiscing about past employers, the infuriating refrain of “at my last job, we…”

Both traps are easy to fall into. When you arrive with fresh eyes, the problems are often genuinely visible. The tech debt is real. The processes are clunky. The organisational structure doesn’t make sense. But what you can’t see yet is why things are the way they are. There are usually reasons, not always good ones, but reasons that matter to the people who’ve been living with them. If you change things without understanding those reasons, you’ll lose trust with the people you need most.

Larson recommends learning through reflection rather than grinding harder. The instinct when you’re new is to work longer hours, attend every meeting, and absorb as much as possible. But learning happens when you process what you’ve observed, not when you’re in constant intake mode. Build in time to think.

What to Learn First

The list of things you need to understand is long, but some things matter more than others in the first 90 days:

The business model. How does the company make money? What are the growth levers? What are the constraints? You can’t make good technical decisions without understanding the business context they serve.

The culture. Not the stated values on the wall, but the actual norms. How do people communicate? How are decisions made? What behaviours get rewarded? What gets punished? This takes time to observe, and you’ll get it wrong at first. That’s fine, just keep watching.

The people. Who are the key players? Who has influence beyond their title? Who’s struggling? Who’s thinking about leaving? Larson recommends a listening tour, if your organisation is under 30 people, meet with each individual privately. As it gets larger, mix team and individual meetings.

The technology. Not just the architecture diagrams, but the lived experience of working with the systems. Larson’s advice to build and deploy a trivial change, do an on-call rotation, and attend incident reviews is excellent. These activities give you ground truth that no briefing document can provide.

The execution patterns. How does work flow from idea to production? Where are the bottlenecks? What’s the release cadence? How are incidents handled? Understanding the existing systems of execution tells you more about the organisation’s health than any metric.

Building Relationships

At a start-up, relationship-building happens naturally because you’re in close proximity with everyone. At a large corporate, it requires deliberate effort. Either way, it’s the most important investment you make in the first 90 days.

Larson emphasises meeting with your peers and stakeholders, not just your team. Two important aspects: getting to know each other as humans, not just as functional roles, and understanding what they need from you and your team. The relationships you build with peers in your first few months will determine how effectively you can collaborate for the rest of your tenure.

With your own team, the priority is listening. Osmani recommends meeting team members individually, assessing current projects, understanding the tech stack, and identifying immediate concerns. But the most important thing is to listen more than you talk. Ask questions. Take notes. Resist the urge to share your opinions until you’ve heard enough to form informed ones.

One thing I’ve learned the hard way: be careful about quick wins. Kambil’s research debunks the “quick wins” myth, stakeholders want “right wins,” not fast ones. A change that looks like a quick win to you might be something the team has deliberately avoided for good reasons. Or it might be something that’s been tried before and failed. Ask before you act.

The Internal Promotion Trap

If you’ve been promoted internally, you face a specific challenge: you already know the organisation, which means you think you understand it. But your perspective has changed, and the things you need to understand are different from what you understood as an IC or a frontline manager.

Kambil observes that internally promoted executives almost always overestimate the quality of their inherited team, because they’re too busy compensating for gaps themselves. You need to step back and assess your team with fresh eyes, which is uncomfortable when these are people you’ve worked alongside.

You also need to give up your old job, something I covered in an earlier article but which bears repeating here. The first 90 days are when the temptation to keep doing your previous role is strongest, because it’s familiar and you’re good at it. Resist. Your new role needs your full attention.

Setting Up Your Support System

Larson recommends three things that I wish I’d done earlier in my career:

Build an external support group. Find people in similar roles at other companies. Not for networking in the transactional sense, but for honest conversation about shared challenges.

Get an executive coach. They’ve seen dozens of people go through what you’re going through, and they’re paid to give you feedback you might not hear from anyone else.

Create space for self-care. The first 90 days are intense, and the temptation is to sacrifice everything personal to prove your commitment. Don’t. You need to invest in yourself so you have the energy to invest in others.

The 90-Day Mindset

The goal of the first 90 days isn’t to transform the organisation. It’s to understand it well enough to know what transformation it actually needs. It’s to build the relationships that will make transformation possible. And it’s to earn enough trust that people will follow you when you do start making changes.

That might feel slow. It might feel like you’re not doing enough. But the leaders who rush to change things in their first month almost always end up spending their second quarter undoing the damage. The leaders who take the time to understand first are the ones who make changes that stick.

Patience isn’t passivity. It’s strategy.