The inventor of this device is still a young engineer.
He was recognized as the planner of the new sales strategy.
開発者 focuses on the developer or creator who brings something to practical use, often in software or product development, whereas 考案者 highlights the original conception.
Compound of 考案 (こうあん, 'plan, devise') + 者 (しゃ, 'person'). The exact historical derivation is uncertain, but the word follows a common Sino-Japanese pattern for agent nouns.