You have some great answers on this thread already. I work with a lot of customers on advising them on scaling infrastructure, data platforms and often times migrating from traditional stacks to some of the newer technologies. There are three aspects to the advice I give customers:
1. In most cases, the new stacks start out as complementary and over time replace the older stack for certain use cases. It's not a complete rip and replace. There are workloads and use cases that are better suited for the LAMP stack and they should stay there.
2. In almost all cases, the migration is limited by the teams' understanding of the new technologies and their comfort level in supporting it with high level of reliability. This turns out to be an education effort as much as a technology migration effort.
3. The overall migration strategy needs to take into account the above two, goals of the overall product, deadlines etc and your advisor should be able to navigate you through these considerations and maybe even help with part of the effort depending on the agreement you have with them.
Hope this helps.