SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '18daa814729a2acc319eef91be9badc39c48df351e3a8963c548926f87949fce' 
  AND token = 'sAzgB1tg4tSxqwdFijWLOwbLFQXSjv05bwEvtdANb9g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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