SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b140e721846d194f844933bd1acaadefff3959c52d6fa5266f678efa5f20f660' 
  AND token = 'eI97SYIhGmh5tTHvKmu3Nz0oRmagZWnAnNJDqCjvyUk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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