SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '6098afcdddd9cfa569f41257e1c3b522e932940398a277fa40e8c868c76e4d89' 
  AND token = 'lnSY0xH/CP52uPhLJV3qEex/+SlC3wZS5zdlxMsfpQE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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