Are there hosted nominatim services that can do all it's duties (particularly reverse-geocoding) all over the world?
We have a high volume of lookups (we dont want to be throttled) but we want to avoid the hassle of hosting Nominatim ourselves.
I had the same issue years ago, I ended up setting up my own nominatim services. It's hard to find a decently priced service. We use a subset (Benelux) of our data since like 90% of the reverse geocodes are withing that area. It's a real maze, most reviews you'll find, there is always one engine they won't cover.
How much volume are we talking about, how many points (per second?) ? I thought about setting up such services on VPS nodes. Once the Database is indexed, you don't really need beefy boxes. Just to serve this data, it's very low overhead in general. It's the indexing that takes a long time. We thought about Geonames but their coverage at the time concerning Europe was not good enough. I find them all very expensive, We saved 12K Euro per year(1600 assets) doing this ourselves (for 5 years ...). It sure pays off at some point, plus the independence you get (ex: a OSM map error you can actually fix within hours). Hope this somewhats helps to decide.
There is an alternative called gisgraphy that use geonames and openstreetmap data. You can install it locally (so cost is 0) or subscribe for hosting (quicker but you have to pay). Some other services are available on the web (mapquest). If you need high relevance, only paid services with premium data as teleatlas or navteq can be used. Openstreetmap is usefull for most common usages but can not be considered as relevant as paid data
I'm a member of the team behind the OpenCage Geocoder, we provide exactly this service. Please have a look: https://geocoder.opencagedata.com
We provide a single, simple API to forward and reverse geocoding for the entire world. The underlying data is OpenStreetMap and various other open datasources. There are libraries for most common programming languages. We offer a free tier and various affordable paid packages depending on usage. Behind the scenes we are using nominatim, but we do a bit more than nominatim, for example formatting the resulting address and adding annotations (things like timezone, etc). We regularly contribute fixes and new features back to nominatim.
I am the marketing head for Geokeo Geocoding api. We provide nominatim service with open street map data and also modifications to resolve data more accurately. We offer 2500 api credits for free tier and also paid tiers are available for large scale deployment. Our api provides forward as well as reverse geocoding.