For production code, in your data models, do you specifiy

@SerialName

for all fields or just the required ones? 1.

data class Foo(@SerialName("_id") val id: Int, @SerialName("name") val name: String)

2.

data class Foo(@SerialName("_id") val id: Int, val name: String)

Yes if proguard is used, no otherwise (i.e. just the required ones) I think.

I only set them where they are required and use the @Keep annotation for proguard.

I prefer using the same

@SerializedName

annotation (even when redundant) when proguard is enabled. I believe that choosing between either

@SerializedName

or

@Keep

is largely subjective though