Blockchain topped online staffing provider Upwork’s second-quarter list of the 20 fastest-growing skills in the US freelance job market for the second consecutive quarter. 

Blockchain — a decentralized way to record information digitally — shows huge potential for businesses, causing a spike in demand for experts familiar with the technology, according to Upwork. Go development, a programming language that can be used to create a blockchain, also appeared on the list at No. 10.

Staffing Industry Analysts reports blockchain, the technology behind cryptocurrencies such as bitcoin, remains very new but could have an effect on staffing — even allowing for autonomous, decentralized staffing firms. SIA examined blockchain in a recent report, “The Impact of Blockchain in Talent Acquisition,” which is available to corporate members online.

The Upwork Skills Index calculates year-over-year growth rates based on freelancer billings through Upwork in the quarter versus the same quarter in the prior year.

The skills categories on the list in the second quarter all experienced more than 150% year-over-year growth; the top 10 grew more than 500%.

The top 20 fastest-growing skills:

1. Blockchain
2. Google Cloud Platform
3. Volusion
4. Risk management
5. Product photography
6. Rapid prototyping
7. Google App Engine API
8. SCORM
9. GitLab
10. Go development
11. Apple UIKit
12. Enterprise architecture
13. Tensorflow
14. Atlassian Confluence
15. Apple Xcode
16. eLearning
17. Customer retention
18. Articulate storyline
19. Node.js
20. Scala development