The phrase "key service" is correct and can be used in written English.
It is often used to refer to a particular important or essential service. Example: "The key service offered by the hotel was their complimentary shuttle to the airport."
"The world of the PC and consumer electronics industry are combining and digital music is becoming a key service".
This Jo'burg to Cape Town train is a key service in South Africa's national passenger network, Shosholoza Meyl.
A private-sector alternative is likely to place pressure on rates of pay for key service staff.
It found that when it comes to key service areas, respondents were concerned that there should not be significant policy variation from place to place.
Mr Maliki hopes that the Sadrists will instead be content with some of Iraq's key service ministries.So the new government has not quite yet been settled.
Indie labels fell out with YouTube in a big way in 2014 over the terms of the contract for its YouTube Music Key service, but particularly when you talk to digital executives from labels, they still see its value.
The low-key service is charmingly accommodating.
With comfortable chairs, inlaid wood tables, subtle décor and low-key service, Cooke's caters to grown-ups, without apology.
The low-key service ended with a Merrill employee, Maryann Montenegro, singing the Mariah Carey song, "Hero," accompanied on piano by Robert Calabrese, a co-worker.
Meals at Japonais were usually herky-jerky affairs, veering quickly from elation to exasperation and undercut by odd pacing and off-key service.
With its comfortable chairs, inlaid wood tables, subtle décor and low-key service, Cooke's is a restaurant that caters to grown-ups and makes no apologies for it.
