I am planning for ACD300 certification so anyone kindly share valid suggestion
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Not sure what you are looking for, but Kunal's blog post is a good source.
https://kunalsharda.com/2021/06/18/appian-certification-program/
What exactly do you want to know?Recently, Appian changed its vendor to ProctorU.The ACD300 seems to be deprecatedEverything properly mentioned here : https://community.appian.com/learn/certifications#prep
The exam code for Appian Lead Developer Certification is ACD301. Here is a page you can refer to, to understand the objectives, expectations as well as topics/resources to clear the exam. All the best!