SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '726002690674a2260b9d259d7bf8117938e4e08f3ab7a95ec68421d759cbc5d6' 
  AND token = '6agfuI5lNPE+vsE/kSURmsgYMrixW+RySKt93kOJtyY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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