As a MLE, how should I communicate with a difficult backend engineering lead?

I’m a machine learning engineer (MLE) working on an e-commerce recommendation system, while our backend engineers manage the serving server. I’m facing communication challenges with the backend lead:

1. We're building an e-commerce search system, but he refuses to use a search engine due to maintenance overhead, insisting a regular database is sufficient for vector search. However, a search engine offers better algorithms, scalability, and faster improvements in click-through rates.

   • (a) Should I just acknowledge his opinion and say I'll bring it back to my team instead of debating in meetings? Because we are discussing the business requirement with PM in that meeting, not focusing on the tech stack.
   • (b) If he still refuses, should I find other collaborators or have MLEs maintain the search engine ourselves?

2. He often shares strong opinions on ML algorithms in meetings, but while 80% is correct, 20% contradicts my understanding. Our discussions are usually focused on system-level topics, if I challenge him, the meeting may go off track; if I don’t, others (PM and other engineers) might assume we agree, leading to misconceptions. How should I handle this?