SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3dff53b44f35a531a922006c9d0391859f14917e242724b06853f5452da9efa5' 
  AND token = 'd76yJPJks1I+JExKFGewhUzSMDEVS+mXzHlWBdHCODg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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