SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7e1e4f994ce5f0b016118828be23afa3e16540381bf0f3947553a2dd972f86d2' 
  AND token = '9WidejRwHmTNuyT7DvWm2sREFOjukEKUkEmUugZHPuQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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