I just finished a big, critical project at work that uses this exact approach with an adjacency list in DynamoDB with 5 GSI's for different access patterns. No

I just finished a big, critical project at work that uses this exact approach with an adjacency list in DynamoDB with 5 GSI's for different access patterns. Not only is it super fast, it's also very extensible. As this article states, however, the most important and hardest part is ensuring your design is correct because you can't really change it once you implement it. You can add features but it's basically impossible to modify an existing implementation. As long as you do the right planning, DynamoDB works great!