SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '14f5dc5988e32da8da34eda9e44d18fb3be769ed232245fa2b0876ff015f2dab' 
  AND token = '35EDXjK29hgUGZ/GBipTxqG7bHFhiVJNxSVCloE0UeY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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