10 Things Developers should know about Databases

1 . 10 Things Developers should know about Databases Peter Zaitsev CEO, Percona Percona University Montevideo April 23, 2019 © 2019 Percona. 1 

2 .Who Are you ? More More OPS ? Developer ? © 2019 Percona. 2 

3 .Ops Focused on Database Only Generalist © 2019 Percona. 3 

4 .Programming Language What Programming Languages does your team use ? © 2019 Percona. 4 

5 .Devs vs Ops DevOps suppose to have solved it but tension is still common between Devs and Ops Especially with Databases which are often special snowflake Especially with larger organizations © 2019 Percona. 5 

6 .Large Organizations Ops vs Ops have conflict too © 2019 Percona. 6 

7 .Devs vs Ops Conflict Devs Ops • Why is this stupid • Why do not learn schema database always the design problem. • Why do not you write • Why can’t it just work and optimized queries work fast • Why do not you think about capacity planning © 2019 Percona. 7 

8 .Database Responsibility Shared Responsibility for Ultimate Success © 2019 Percona. 8 

9 .Top Recommendations for Developers © 2019 Percona. 9 

10 .Learn Database Basics You can’t build great database powered applications if you do not understand how databases work Schema Design Power of the Database Language How Database Executes the Query © 2019 Percona. 10 

11 .Query Execution Diagram © 2019 Percona. 11 

12 .How are Queries Executed ? Single Threaded Single Node Distributed © 2019 Percona. 12 

13 .Indexes Indexes are Indexes are Must Expensive © 2019 Percona. 13 

14 .Capacity Planning No Database can handle “unlimited scale” Scalability is very application dependent Trust Measurements more than Promises Can be done or can be done Efficiently ? © 2019 Percona. 14 

15 .Scalable != Efficient The Systems which promote a scalable can be less efficient Hadoop, Cassandra, TiDB are great examples By only the wrong thing you can get in trouble © 2019 Percona. 15 

16 .TiDB Scalability (Single Node) © 2019 Percona. 16 

17 .TiDB Efficiency © 2019 Percona. 17 

18 .Throughput != Latency If I tell you system can do 100.000 queries/sec would you say it is fast ? © 2019 Percona. 18 

19 .Speed of Light Limitations High Availability Design Choices You want instant durable replication over wide geography or Performance ? Understanding Difference between High Availability and Disaster Recovery protocols Network Bandwidth is not the same as Latency © 2019 Percona. 19 

20 .Mind Network Latency © 2019 Percona. 20 

21 .Also Understand Connections to the database are expensive Especially if doing TLS Handshake Query Latency Tends to Add Up Especially on real network and not your laptop © 2019 Percona. 21 

22 .Law of Gravity Shitty Application at scale will bring down any Database © 2019 Percona. 22 

23 .Scale Matters Developing and Testing with Toy Database is risky Queries Do not slow down linearly The slowest query may slow down most rapidly © 2019 Percona. 23 

24 .Memory or Disk Data Accessed in memory is much faster than on disk It is true even with modern SSDs SSD accesses data in large blocks, memory does not Fitting data in Working Set © 2019 Percona. 24 

25 .Newer is not Always Faster Upgrading to the new Defaults Change are Test it out Software/Hardware often to blame is not always faster © 2019 Percona. 25 

26 .Upgrades are needed but not seamless Major Database Upgrades often require application changes Having Conversation on Application Lifecycle is a key © 2019 Percona. 26 

27 .Character Sets Performance Impact Pain to Change Wrong Character Set can cause Data Loss © 2019 Percona. 27 

28 .Character Sets https://per.co.na/MySQLCharsetImpact © 2019 Percona. 28 

29 .Less impact In MySQL 8 © 2019 Percona. 29