Which concepts do newcomers to Rust struggle with? 

- Lifetimes, especially static and serde deserialzer
- Traits vs classes
- Dynamically sized types
- Object safety
- Sum types

What else?

Rust + decentralized databases. I have one goal in life: the ability to stop thinking at will

Building TokenOps.xyz - token distribution 

Dealing with packaging and entirely awful crates registry

Safe Multithreading using Send + Sync and how to properly use it without too many tries🙈

perhaps not relevant to newcomers, but pinning can be difficult to grasp at first

Async rust, Futures, Executors, Pins, Traits with sync and async functions