I've always seen these kinds of questions on the forum.
GoogleMaps, Yandex, Mapbox, Here, Bing Maps, locationIQ, MapQuest, graphhopper, Opencage, etc.
They all have limits on their geocoding services and API usage latencies (amount x time).
You should roughly estimate the range of requests per day and time that your application would have and select the most convenient alternative from geocode service providers.
Nominatim does not have limetes in geocode requests, but it does in the concurrence of requests per seconds.
operations.osmfoundation.org
P.S:
Nothing is free in this life
Cheers,