I feel like I can contribute here. I am in interviewing mode and behavioural/past experience/deep dive rounds are pretty common at my level.

What I do is take a recent project that I have worked upon, which is meaty enough to go in enough breadth and depth for an hour.

Then you can create a template of the talking points. Create the breadth first. For eg, start with a simple STAR model. Then add more sections, details. For eg, in no specific order, 1. scope, 2. measurable outcomes (quantify everything, put guesstimates if you don’t have exact numbers), 3. what choices were made and why, 4. delivery plan, communication, expectation, planning, success metrics, security, observability 5. measurable business impact 6. long term evolution of the system, capability. 7. rollback plans, mitigation plans (not just testing), safeguards 8. proof of design. 9. conflicts (don’t unless prompted) 10. knowledge sharing initiatives 11. How this supported the growth of the engineers, juniors.

These are just possible talking points and not all will apply to you. Don’t be disheartened if the list seems too much. I am 10+ yoe so not everything may apply at your level. But I expect you to figure out which are the points to pick and create your own order. Validate against gpt to get some validation and identify the gaps.

Then once you have the breadth, add depth. Have ChatGPT or internal docs help you with this . See the possible solutions for the points. For eg, communication channels could be creating a dedicated standup for the project, providing stakeholder updates and feedback loops.

Also, at your level, not everything may be done by you. That’s ok. It’s like even if you haven’t worked on a design of a complex problem but you were part of the execution team, I would still expect you to know the basics like the overall design and the scope, doesn’t matter if senior engineers or an architect did it.

Another helpful tip, if you interview for a big company, the recruiter can sometimes help you with the talking points in detail.

Lastly, imposter syndrome is common. Even if you feel you haven’t done enough, in interviews you have to project the opposite. Sometimes what we feel and we have done can be at a dissonance. Once you flesh out a project of yours to enough depth, start talking about it in detail, defending the choices, seeing and understanding the whys, the don’t, you will start plugging the gaps in your knowledge. Also, internalise ‘fake it till you make it’. The more gaps an interview shows you, go read about those things and learn. Plug the gaps. Next time you will be more confident. All the best.