The phrase "according to key" has several synonyms that can be used interchangeably in different situations. Some of these synonyms include "as per", "in line with", "consistent with", "in accordance with", "following" and "based on". These phrases are often used when referring to a particular source or standard and help to indicate that the information is reliable and accurate. Essentially, they all convey the same meaning, which is that something is being done or said in a manner that aligns with a specific criteria. Using these synonyms interchangeably can help to add variety to your writing and make your content more engaging.