The opportunity solution tree (OST) was invented by Teresa Torres as a means to collect and visualize the opportunity space. It is a model or mental representation that clearly links product goals to user needs and to the options for solving those needs. In product discovery, it is a powerful tool for creating a clear structure of what the team wants to achieve.
In its essence, agile product development is a mindset for dealing with an uncertain environment. The best way to do that is to find the path forward one step at a time. This means delivering frequently, observing how users react and interact with the product, and adjusting the approach for the next iteration according to the feedback and observations. Scrum is the manifestation of exactly this approach within a project management method.
To me, the sprint review is an extremely valuable ceremony. The principles behind the session itself are powerful, universally true, and can be applied outside of Scrum as well. Nevertheless, I feel that the goal and the importance of the review is sometimes misunderstood.
Can Scrum and a Scrum team work without a Scrum Master? The short answer is yes. I believe it is possible. The longer answer is a bit more complicated. The Scrum Master Role was created for good reason and not having one will lead to some negative effects.
It generally seems to be the case that we have too many ideas for improvements but not enough time to do them all right away. Therefore, backlogs tend to become large. In order to be able to handle this, it is so important to organize the backlog in a structured way.
In general, it seems most people agree that remote work is a net positive but it also poses some challenges. Very underrated are the effects of remote work on company culture. The challenges to building a real team are probably more obvious. Nevertheless, I feel they are worth addressing.
Besides the retrospective, the backlog refinement (sometimes called grooming) is in my view the most important ceremony within the scrum framework. One could even argue that it is the most important one. It certainly has an outsized positive impact on team productivity, created value, and team chemistry - if done correctly.
Slicing requirements horizontally instead of vertically, it sounds so easy but is so hard to do in practice. It is, in my view, one of the main features of agile that unlocks team productivity.