SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c76390262bd7fa17f5ec69591d1cca6979df58381973eca7a1ba4942500c0dd6' 
  AND token = 'ZddMPG3gtNZmrrIQkD9P7oXRUKhl1jCBQWHixO5lQjk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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