SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '208db75f57c2f94e572b362eced1da2295ee3abbd18141bfd034aa41df98fa47' 
  AND token = '5TlNRCl1oKQNff8sUhKTX299vuOc2K8bWXteN968Tns=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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