You might also be interested in checking out our JSON localization tutorial (aimed towards web devs).
Lokalise supports flat JSON files. Here is a flat JSON file example:
{"app.name":"Lokalise","app.description":"Nice service"}
If you are using TypeScript and want to add autocompletion feature for your key names, you can add the following line of code to your app:
keyof typeof import ('./path/to/some/json/file.json')