Rails API with query string time stamp

I am continuing on creating an API with ruby on rails. I have got the basis of it done by following https://levelup.gitconnected.com/7-steps-to-create-an-api-in-rails-2f984c7c4286

but instead of Forests and trails, I am using restaurants and Comments as my models. Restaurants has many comments and comments has one restaurant.

Right now I can call on: http://localhost:3000/api/v1/restaurants/1?by_updated_at=2022-08-20T10:00:00.000Z

This will send me the exact comments that updated at that given time.

[
    {
        "id": 1,
        "restaurant_id": 1,
        "comment": "good.",
         "age": 28,
        "created_at": "2022-08-20T10:00:00.000Z",
        "updated_at": "2022-08-20T10:00:00.000Z"
    }
]

I would like to go further and say if the user wants to find the updated time of a comment for restaurant 1 like: http://localhost:3000/api/v1/restaurants/1?by_updated_at=2022-08-20T12:00:00.000Z AND there is no record with the exact updated_at time given:

How do I get the record that is closest to it? So that the record shown is then:

    {
        "id": 2,
        "restaurant_id": 1,
        "comment": "very good.",
         "age": 25,
        "created_at": "2022-08-20T12:30:00.000Z",
        "updated_at": "2022-08-20T12:30:00.000Z"
    }
]

Right now my code looks like: restaurants_controller.rb

  def show
    @restaurant = Restaurant.find(params[:id])
    @comments = apply_scopes(@restaurant.comments).first
    render json: @comments
  end

comment.rb (model) with

gem 'has_scope'

class Comment < ApplicationRecord
  belongs_to :restaurant
  scope :by_updated_at, ->updated_at { where(updated_at: updated_at)}

I looked at the first answer of this one: How to pass query params to Rails API controller? in combination with: find record closest to a given time in ruby on rails

and thought maybe I need to be updating the scope in the comment model to do something like this

  scope :by_updated_at, ->updated_at { where('updated_at>= ? AND updated_at <= ?', updated_at - 600, updated_at + 600).order('ABS(updated_at - updated_at)'), updated_at }

this is obviously wrong but now I am confused by the many updated_ats and not sure how to implement

note: there are many more records in this.