SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'dfe729b7ebbc70e8f510652e0625f429de6f8e4e822138f599fa41faf2263c3d' 
  AND token = 'KLmcsVB09kdB1zfISv5vCwgQDpV9GZ1X/jxABjNBy0M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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