SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8348854334e174c667b5b9364ff62deebf513230749cd34a49020a8d7a04705f' 
  AND token = '29NcxhOnXINqe0dUo9gm29KgHaKK/rzIiEc3mO9zaxU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}