Lessons from working on WordPress.com

WordCamp Romania 2014

About me

● Veselin Nikolov● @dzver● WordPress.com

About me

● Background as MS SQL DBA

● Currently trying to keep things simple in a team of 10

What happened with the MySQL talk

One month ago

The reception

The questions

● How do I make WordPress secure● What are your tips for secure WordPress● How do I chose save plugins and themes● How do you manage to work remotely?● Are there any other Bulgarians at Automattic?

! MySQL

There are no mistakes,only lessons.

Lesson learned

● Another set of lessons this time and we'll see which one worked better :-)

Story #1 The ID

● 7 year old legacy code● Entire table described in the code● We have items with ids 5 and 6. We need to

add 7.

Story #1 The ID

● One new object● A few helpers● 135 removed magic numbers● One changeset● 0 unit tests

● What could possibly go wrong?

Story #1 Lessons

● Pleasepleaseplease, no magic numbers● Atomic commits, please!● Long functions are hard to understand● Stats monitoring● Legacy is code for which we don't have tests

Story #2 The Notification

● Montreal● 1+ million emails● 1+ million discount coupons (10-ish previously)● Friday

● What could possibly go wrong?

Story #2 The Notification

● Queries that work with small tables:

SELECT * FROM table

SELECT * FROM table ORDER BY whatever

LIMIT 200, 100

Story #2 The Notification

● Queries that don't work with large tables:

SELECT * FROM table

SELECT * FROM table ORDER BY whatever

LIMIT 200, 100

Story #2 The Notification

● Fetching big amounts of data breaks things● Offsetting breaks things● The coupons weren't really used in the past● Repeating millions of anything means a lot of

time

Launching big things on Friday

Offsets

SELECT * FROM ...

WHERE `id` > 1093029

ORDER BY `id` LIMIT 20

SELECT `deadline` FROM ...

WHERE `date` BETWEEN '2014-06-20' AND ...

Offsets

SELECT * FROM ...

WHERE `id` > 1093029

ORDER BY `id` LIMIT 20

SELECT `deadline` FROM ...

WHERE `date` BETWEEN '2014-06-20' AND ...

Offsets

SELECT * FROM `table` JOIN (

SELECT `id` FROM `table`

ORDER BY `whatever`LIMIT 5000,50

) as `b` USING `id`

Story #3 The A/B Test

● A/B test is showing different things to users and measuring effect

● We use Kissmetrics

● We've had 5 different A/B testing classes

Story #3 The A/B Test

● Feature-rich classes● Many levels of abstraction● Expressive names● Many filters and actions

● What could possibly go wrong?

Story #3 The A/B Test

● Wrong results, no one knows why.

Story #3 Lessons Learned

● KISS. Simplest solution worked● Kissmetrics rocks● A/B test everything

Story #4 Barry

<bazza> howdy

<dzver> hi, did I break anything?

<bazza> your blog looks hacked

Story #4

● Unique passwords● 2-factor auth● Come to WordCamp Europe and maybe watch

Barry live :-)

● #praythatbarrycomestowceurope

Summary

● KISS. Simple queries. Simple code.● DRY. Repetition fails.● A/B test. Unit test. Test!

● Launch your next project on Friday at 7pm.

My name is VeselinI code for food.

Ask me anything!