Question - MongoDB for Time Series Data: Schema Design

question.md

How this schema is possible in JSON?

{
  speed: { 0: 63, 1: 58, .., 58: 66, 59: 64}
}

Because... you know... EMACS... first char cannot be a number.

Or I should read like this?

{
  speed: [ [0, 63], [1, 58], .., [58, 66], [59, 64] ]
}