SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'd4b15d109b61af12a32508d5a63832948f990cec6766c874a66f5659a17f3b5b' 
  AND token = 'G5fj4q7uPphIG4ChloLkf1IBtJ+tTTWhjYKom/y8km0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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