SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6fc9be3d70967f35ebeb6306268e8c979dd7cf8b14a7fe9a4ea8f7a3f0210c03' 
  AND token = 'GjiqkcYx5c3EOblAg5g0qu1Bm+VegW3Keg4jshca8Rc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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