SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dad9f5fcdeed5c5f805f37c254a3b55581c203e87d8f990343699fe1b9b7ba19' 
  AND token = 'fI/TWj2mGIjRTILkZBB9UELgrLYsRhx+2hrZtBhQV+g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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