mysql row expiry strategy

expiry.sql

CREATE TABLE things (
 id int NOT NULL AUTO_INCREMENT PRIMARY KEY,  
 created timestamp NULL DEFAULT CURRENT_TIMESTAMP,  
 str varchar(10),
 expires timestamp 
);

INSERT INTO things (str) VALUES ('one');

CREATE TRIGGER set_thing_expires
    BEFORE INSERT ON things
    FOR EACH ROW
    SET NEW.expires = ADDDATE(CURRENT_TIMESTAMP, INTERVAL 30 DAY);

INSERT INTO things (str) VALUES ('two');

SELECT * FROM things; 
+----+---------------------+------+---------------------+
| id | created             | str  | expires             |
+----+---------------------+------+---------------------+
|  1 | 2023-07-23 15:11:53 | one  | NULL                |
|  2 | 2023-07-23 15:11:53 | two  | 2023-08-22 15:11:53 |
+----+---------------------+------+---------------------+

SELECT now();
+---------------------+
| now()               |
+---------------------+
| 2023-07-23 15:12:02 |
+---------------------+

SELECT id FROM things WHERE expires > now();
+----+
| id |
+----+
|  2 |
+----+


DROP TRIGGER set_thing_expires;

CREATE TRIGGER set_thing_expires
    BEFORE INSERT ON things
    FOR EACH ROW
    SET NEW.expires = ADDDATE(curdate(), INTERVAL 30 DAY);

INSERT INTO things (str) VALUES ('three');

SELECT * FROM things; 
+----+---------------------+-------+---------------------+
| id | created             | str   | expires             |
+----+---------------------+-------+---------------------+
|  1 | 2023-07-23 15:11:53 | one   | NULL                |
|  2 | 2023-07-23 15:11:53 | two   | 2023-08-22 15:11:53 |
|  3 | 2023-07-23 15:12:47 | three | 2023-08-22 00:00:00 |
+----+---------------------+-------+---------------------+

/* renew item; update expiry to thirty days from renewal action */
UPDATE things SET expires=ADDDATE(curdate(), INTERVAL 30 DAY) WHERE id=3;

SELECT things.*, UNIX_TIMESTAMP(things.expires) AS expires_stamp FROM things;