SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c223863a303b8fd87221eca3fd11d7fbab09cd9148151beddeea43c007389d6f' 
  AND token = '6MYZgexPfW4oWAqPPBOyKNjaxbo1IHvRbUNdiwzR1PU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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