SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c3b6fa0e1be647b7ba135099fdc35c05c480f0e535951a5850e21afab05fffb4' 
  AND token = 'xAVUKel7CNqDmnKyrZ/00AJt/86RYIuf4YJPGML0UUk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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