SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21d7f8853d23a6d672f831a6a4b3d5aac36f6a096461afb7ff066098ecf0d07b' 
  AND token = 'n2a9tmnMpmQjVLEBhEg1mcmEVo6syx2zPnIWTRrOtGY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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