当然可以。考研英语小作文一般要求篇幅在100-120词左右，90字是完全可行的。关键在于条理清晰、言简意赅地表达观点。以下是一个90字的小作文示例：
Dear friends,
I am writing to express my gratitude for your invitation. Unfortunately, due to my tight schedule, I am unable to attend the party. However, I sincerely wish you all a joyful and memorable celebration. Thank you for considering me.
Best regards,
[Your Name]
【考研刷题通】微信小程序，全方位考研刷题利器，政治、英语、数学等科目一网打尽，助你高效备考，轻松征服考研！立即体验，开启你的考研之路！🎓📚📈