Pros
Growth Intelligence allowed me to grow massively as a developer from junior to team lead. Working in a small company really gives you exposure to a wide variety of experience - from working across the full development stack (and then some... super-stack developer?) to designing elements of the UI to travelling to meet users. Additionally, being a small company everyone is very close, which is great because everyone is very friendly. Except surreal lunch conversations with the leadership team, full company dinners and activities, lots of mixing with people across departments. As a developer working with Prash (CTO) was great, he's an experienced developer and now after many year also an experienced CTO! The way he's set the team up shows he cares about both business goals and personal development. Being a machine learning company, even if you're not one of the data scientists you'll see the full lifecycle of a machine learning model and work on the data and model management aspects, which in my opinion is just as interesting and a highly sort-after skill. To cap it all off - the company has really found a good product-market fit, which is demonstrated in the growth numbers for the last year. So a very exciting place to work which will bring many new opportunities to grow into new roles.
Cons
If your goal is to focus on one very specific area - a small team is not for you. Expect to be working on a variety of areas, making gradual improvements. If your goal is to work in 5 different programming languages - this is not for you. Growth Intelligence primarily work in Python (for the data-science stack). Using other languages is possible (the UI is a react application for example) but the pragmatic choice is often to stick with Python. If your goal is to work on a large scale distributed system with dozens of microservices, this is not for you. Its not that type of company (not B2C for a start). If your goal is to get paid a gazillion pounds, this is not for you. Its a startup, and not one that is guzzling more venture capital money than is sustainable.