Searching: Elasticsearch, Algolia, or building your own? What works best?

hey everyone, im tryin to figure out the best way to add search to our new product. we expect lots of dynamic data and need fast, relevant results. ive been looking at services like Elasticsearch and Algolia, but im also wonderin if buildin something custom on a database index might work for us. what are your experiences with these? any hidden gotchas or advice on when to pick one over the others?