This is a complex topic. There are different criteria amongst different analysts, developers and architects. My suggestion is to sit with your team and define the standard that fits you best. Said that, in my personal opinion I would consider the following:
Low Complexity
- Linear processes with little to no variants
- Simple rules and calculations
- Achievable with the Out of the box activities provided with the tool
- Small amount of applications to be automated (2-3)
Medium Complexity
- Processes that have well definded variants
- Processes that involve generating reporting from medium data sources
- Basic database usage
- Using scripts/invoke code is required for small and specific scenarios
- Basic API calls
- Basic integration with other UiPath services (i.e. document understanding)
High Complexity
- Build complex DB queries
- Usage of third-party libraries (code level)
- High security-compliant processes (encryption, hash, modern authentication)
- Complex business rules
- advanced orchestration
- Leverage of machine learning
Again, this is my personal opinion and there might be some gray areas and flaws in it. I’m also adding another forum post that may be helpful. Also, I strongly recommend you to take the academy Solution Architect training for additional understanding of architecture and more insight on estimations.
Calculating actions (Estimating complexity of a process) - Help - UiPath Community Forum