SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76ec3d69d0db53dd83882cf780209cb4d84b31008dec7589d640f4298d37d894' 
  AND token = 'omEv1nACUFaFwgf29q7S9DUMqd6NWGfajTDUYDNIczY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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