Effective Startup Engineering

Guest Lecture at "Startup Engineering" (Stanford CS184 / Coursera class)

1. Ian Wong • Square Inc. coursera.org/course/startup EFFECTIVE STARTUP ENGINEERING 1
2. An effective sta up engineering team ships useful and delightful products to the customers at a fast pace. ef·fec·tive /iˈfektiv/ 2
3. Square makes commerce easy for everyone. 3
4. Enable anyone to accept credit card payments anytime, anywhere. 4
6. Analytics that enable small businesses to compete (and win). 6
8. Momentum ‣ Square is currently processing more than $10 billion in payments annually. ‣ In 2012, we grew our customer base from 1 million to 3 million. ‣ There are more than 250,000 businesses listed in the Square directory. ‣ Square readers are now available in nearly 40,000 retail locations nationwide. ‣ Square’s transaction volume makes it the equivalent of the 20th largest retailer in the United States. 8
9. Who’s this dude? Ian Wong Inference Scientist ‣ Stanford BS EE 08, MS EE 09, MS Stats 10, PhD Dropout 10 ‣ Square Risk Team ‣ Machine learning system to assess and mitigate risk of entities and events in our network ‣ Visualization and workflow tools for operational specialists to review customer accounts 9
10. Design for modularity Learn to test Use and contribute to open source Foster an open, collaborative and responsible culture 10
11. Design for modularity Learn to test Use and contribute to open source 11
12. Simple Made Easy Rich Hickey 1. We can only hope to make reliable those things we understand. 2. We can only consider a few things at a time. 3. Inte wined things must be considered together. 4. Complexity undermines understanding. http://www.infoq.com/presentations/Simple-Made-Easy 12
13. You want to avoid this 13
14. Let’s talk about your god class 14
15. Let’s talk about your god class ‣ Does it do everything? ‣ Harder and harder to add functionality? ‣ Things feel tangled? Lots of states and side effects? 15
16. Extract a Service Class Tip: Stop adding functionality to your model or controller. Create a service class. 16
17. Extract a Service Class 17
18. Micro to Macro ‣ Loosely coupled, well-encapsulated service classes within a code base interact with each other via simple inte aces. ‣ Loosely coupled, well-encapsulated services within a service oriented architecture interact with each other via simple inte aces. 18
19. Life of a Payment Payment Processing Risk Assessment Settlement An individual service can grow in complexity without being concerned with other services. 19
20. Separation of Concerns Payment Processing Settlement Gandalf Orchestrator RiskArbiter Decider Regulator Customer Review Tool SignalService Real-time risk signals computation ModelKit Batch ML model training 20
21. Source: Simple Made Easy, Rich Hickey. Speed Time Easy Simple 21
22. Design for modularity Learn to test Use and contribute to open source 22
23. Design for modularity Learn to test Use and contribute to open source Foster an open, collaborative and responsible culture 23
24. Fast Test, Slow Test Gary Bernhardt The three goals of testing: 1. Prevent regression 2. Prevent fear 3. Prevent bad design http://www.youtube.com/watch?v=RAxiiRPHS9k 24
25. ‣ Introduce change that will not unexpectedly break what you have. ‣ “If you don’t test your code, your customers will” (Pragmatic Programmer). Prevents Regression ............................... Finished in 0.10664 seconds 66 examples, 0 failures 25
26. ‣ Refactor with confidence. ‣ Tests as documentation. ‣ Tests as contracts. Prevents Fear describe Admin::RefundsController do describe “#approve” do let(:refund) { Factory(:card_refund, :status => refund_status, :review_comment => review_comment) } let(:review_comment) { nil } let(:refund_status) { :requested } let(:call_controller) { put :approve, :id => refund.to_param, :review_comment => “cuz!” } let(:user) { Factory(:user, :role_name => role_name) } let(:role_name) { risk } before { user_login user } it “approves and completes the refund request” do call_controller response.should redirect_to(admin_refund_request_url) flash[:message].should == “Refund completed.” refund.reload.should be_completed refund.review_comment.should == “cuz!” end 26
27. Prevents Fear describe Risk::RefundProcessor do let(:admin_user) { Factory(:admin_user) } let(:refund) { Factory(:card_refund, :status => refund_status, :review_comment => review_comment) } let(:review_comment) { nil } let(:refund_status) { :requested } describe “.approve” do it “should return true and leave the refund’s status if it is completed” do refund.status = :completed refund.should_not_receive(:process!) Risk::RefundProcessor.approve_and_process(admin_user, refund, nil).should be_true end end end ‣ Refactor with confidence ‣ Tests as documentation ‣ Tests as contracts 27
28. Prevents Bad Design Source: Growing Object-Oriented Software, Guided by Tests Refactor Write a failing acceptance test Make the test pass Write a failing unit test 28
29. Types of tests Source: Misko Hevery, Clean Code Talks. ‣ Acceptance: Tests whole application. Mostly happy paths. ‣ Integration: External dependencies simulated. Tests class interaction. ‣ Unit: Focus on application logic. Fast! Quick feedback! Execution time Amount of feedback Number of tests Unit Integration Acceptance 29
30. Drives Design: Demo Gandalf Orchestrator RiskArbiter Decider Regulator Customer Review Tool SignalService Real-time risk signals computation ModelKit Batch ML model training Let’s build Gandalf. 30
31. Resources 31
32. Design for modularity Learn to test Use and contribute to open source Foster an open, collaborative and responsible culture 32
33. Design for modularity Learn to test Use and contribute to open source Foster an open, collaborative and responsible culture 33
34. Develop an Open Source Philosophy ‣ Square is built upon open source. ‣ Many developers are active contributors to open source software. ‣ Build what you need to deliver value. ‣ When you must, invent and open source. ‣ Build your brand. 34
35. ‣ KIF (Objective-C): Keep It Functional - An iOS functional testing framework. ‣ Cane (Ruby): Code quality threshold checking as pa of your build. ‣ Dagger (Java): A fast dependency injection framework for Android and Java. ‣ Cubism (JS): A JavaScript library for time series visualization. ‣ Squash (x-platform): A library for exception tracking and bug repo ing. Square’s Open Source Projects Sampling from github.com/square 35
36. Cubism Source: http://square.github.com/cubism/ http://bost.ocks.org/mike/cubism/intro/demo-stocks.html 36
37. Cubism 37
38. Design for modularity Learn to test Use and contribute to open source Foster an open, collaborative and responsible culture 38
39. Learn to test Use and contribute to open source Foster an open, collaborative and responsible culture 39
40. Transparency Ingredients to an Effective Sta up 40
41. Engagement Ingredients to an Effective Sta up 41
42. Responsibility Ingredients to an Effective Sta up 42
43. ‣ Instant code and design feedback. ‣ Learn from one another. ‣ Fastest way to onboard new hires. ‣ No excuse to check Twitter. ‣ “Pairing on a problem” is a common parlance. Pair Programming 43
44. ‣ Code reviews ‣ On-call rotation ‣ Postmo em ‣ Retrospectives Engineering processes Source: http://www.youtube.com/watch?v=AajAVNr73tg 44
45. Design for modularity Learn to test Use and contribute to open source Foster an open, collaborative and responsible culture 45
46. What You Should Do Later Today ‣ Extract a service class ‣ Write a test before you implement ‣ Pair program with your teammate 46
47. It’s okay if you didn’t catch everything. We’re hiring. jobs.squareup.com 47
48. ian@squareup.com @ihat 48