active_model_serializers/cruft.md

As of Ruby 1.9.3, it is impossible to dynamically generate a Symbol through interpolation without generating garbage. Theoretically, Ruby should be able to take care of this by building up the String in C and interning the C String.

Because of this, we avoid generating dynamic Symbols at runtime. For example, instead of generating the instrumentation event dynamically, we have a constant with a Hash of events:

INSTRUMENT = {
  serialize: :"serialize.serializer",
  associations: :"associations.serializer"
}

If Ruby ever fixes this issue and avoids generating garbage with dynamic symbols, this code can be removed.