If someone has gone out of their way to do a good job, here is a sample template you can use to write a letter of commendation for outstanding service.
To,
[Name]
Dear, [Name]
I would like to extend an abundance of gratitude for your meritorious service. Your commitment to this end has been outstanding and effective. I sincerely thank you for your efforts.
I hope you manifest your talent in similar ways in the future. Thanking you again.
Sincerely,
[Name]