SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ef367d758bb5ecd0598b409cdda96259843442391475d851e8afdd1b77bc55c3' 
  AND token = 'ELMaR1YMPTYURs+x3Zu6pD9lJa2Vmvb/TsOYV1NICrI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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