Leon was active only in the year 2005, which was obviously a prolific year for him, at least as far as Rails is concerned. These days, according to his blog, he puts more time into Rust, Go, and Node.js. His commits show a very consistent theme: Leon contributed substantial work to Action Web Service, an early (pre-REST!) web services library for working with SOAP, WSDL, and XML-RPC.
Action Web Service is now defunct. Rails adopted a REST strategy in 2006 that came to totally redefine how web applications built, provided, and consumed APIs, and REST itself may be fading out of use in favor of GraphQL these days. However, back in the day, SOAP and other early web API technologies were in heavy use, and by helping to provide support for them in Rails, Leon helped Rails achieve the legitimacy in large companies which was necessary for it to achieve widespread adoption. So although you’re unlikely to use many of Leon’s commits in your day-to-day work with Rails, the fact that we have day-to-day work with Rails is partly due to his contributions. So, a big shoutout to Leon for the old-school API support.
Raimonds was active from 2009 to 2011. There’s a theme in his commits as well: except for a couple spec files, all of Raimonds’s commits are in ActiveRecord or ActiveRelation. He’s also the creator of several database-related gems, including two which provide Ruby support for Oracle PL/SQL procedures, and unit testing them. Like old-school web services, support for “enterprise” databases like Oracle was very important for Rails’s credibility at big companies in the late 2000s. Open source databases like PostgreSQL and MySQL were still viewed, at that time, as less serious and professional than their enterprise counterparts. Even today, the extended processing capacities unlocked by Raimonds’s Mondrian OLAP gem go beyond what you’d see with the typical Postgres install. So a big thank you also to Raimonds for his work.