Localization and targeting of content in multilingual SharePoint installations is always an issue. SharePoint offers a multitude of ways profile content based on user language (or other properties), but none of the solutions are fool proof. This post describes how to fetch only localized results from SharePoint Search index, which solves at least some of the issues.
SharePoint Search index can be used in quite a few different ways. Probably the most typical way is by searching on SharePoint, or using webparts like Content Search or Content Results. However, one can also build custom functionality, custom client-side liftups, webjobs, single-page applications, mobile applications and a ton of other things that fetch data from SharePoint search index. However, on multilingual tenants, results are, by default, not localized at all. That means, that typically everyone will get the highest-ranking results back, despite them being in the wrong language. And that’s one of the many, many ways to annoy your users!