SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ac7fef71109b794370ce98d4f5dc5e3192a6bb8a650426a88e4b18b6941bf313' 
  AND token = 'QBrxJAob5oymaPe3k8NULcIiU2/E3ohDlgWIYLky44w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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