SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6e29e62ab788401c9781288820e679faaac52071d7b9ab3472b812531bda8a88' 
  AND token = 'gvRXG0UpD7brRVN8OiTttIMERNGc+bTUnXn6P3LofnE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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