Is the monolith a problem? - RubyConf India 2025

presented at RubyConf India 2025

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Transcript

1. Is the monolith a problem? Chikahiro Tokoro
2. Shape the Future of Business Travel The first Travel and Expense Management solution that truly digitally maps all areas of a business trip from end to end. From booking to invoicing!
3. The monolith was blamed for last decade… Not scalable Complex and hard to debug Deployment bottleneck Not clear boundary Difficult to maintain
4. The monolith was blamed for last decade… Not scalable Not clear boundary Difficult to maintain Deployment bottleneck Complex and hard to debug
5. ….and is the microservices a solution? ✅
6. Tobi Lutke (Shopify co-founder) - X Is the monolith, not scalable?
7. Is the monolith, deployment bottleneck? Interpreters Everywhere and All the Time - Stefan Marr, PLISS 2023
8. And Is the microservices, simple and easy to maintain?
10. BBC NEWS | UK | Magazine | The life cycle of a fashion trend
11. 2014 2025 2004 1998 2014 2006 2008 2002 2016
12. Macro trends in the tech industry | April 2024 | Thoughtworks
13. Scaling up the Prime Video audio/video monitoring service and reducing costs by 90% - 2023 Freedom Dumlao on X - 2024.09
14. Rails World 2023 Opening Keynote - David Heinemeier Hansson The End of Programming as We Know It - Tim O’Reilly AI boom masks fundraising struggles for non-AI startups - Techcrunch
15. Monolith / Microservices are the architectures which has own pros and cons
16. CI / Deployment Language Monolingual Multilingual Slow Fast Simple Complex Infrastructure Latency Tracing Scaling Boundary Low High Single instance Multiple instances Clear Vague scale up (vertical) high cost, limited, Inefficient scale out (horizontal) low cost, unlimited, efficient
17. Building Microservices, 2nd Edition - Sam Newman: 1. What Are Microservices? - Should I Use Microservices? 2000 engineers, 2 millions lines of code: the history of a Rails monolith - Cristian and Anatoly | EuRuKo 2024
18. Is the monolith a problem? No Then what’s the problem?
19. Jason Warner (Github ex-CTO) - X
20. Modular Monolith
21. What’s the modular monolith? InfoQ: Monolith Decomposition Patterns - Sam Newman
22. Shopify/packwerk: Good things come in small packages
23. 2014 2025 2004 1998 Macro trends in the tech industry | April 2024 | Thoughtworks Modular Monolith
24. 2014 2025 2004 1998 Macro trends in the tech industry | April 2024 | Thoughtworks Modular Monolith
25. Eileen Uchitelle - The Myth of the Modular Monolith - Rails World 2024
26. High cohesion is necessary
27. God Object
28. This is a problem! God Object
29. Tight coupling / Poor cohesion Antipattern: Single object knows/does too much What’s the God Object (Class) ? Hard to change, buggy Not clear boundary / Tangling e.g. Changing User Registration logic break Payment feature 😱
30. Example of God Object
31. Not scalable Deployment bottleneck ✅ ✅ The monolith was blamed for last decade… Difficult to maintain Complex and hard to debug Not clear boundary Those are characteristics of God Object!
32. 2. Refactoring God Object 1. Better Model Design Where the God Object come from?
33. DRY ~ Don’t Repeat Yourself ~ “Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.“ NOT for the code!! 1. Better Model Design
34. Invoice Receipt Customer understand DRY Let’s DRY for duplicated code!!
35. understand DRY Customer Document type: invoice / receipt Invoice Receipt Receipt should be issued after invoice was paid use STI
36. understand DRY Customer Invoice Receipt Invoice can only be issued for company Document type: invoice / receipt
37. understand DRY Customer Invoice Receipt Company After issuing invoice, it should generate PDF Document type: invoice / receipt
38. Document type: invoice / receipt understand DRY Customer Invoice Receipt Company pdf
39. understand DRY Customer Invoice Receipt Company pdf Document type: invoice / receipt
40. understand DRY Invoice Receipt Customer This is a similarity! Code duplication might be coincident Invoice and Receipt are different (domain) knowledge
41. understand DRY Customer Invoice Receipt Company pdf
42. 1. Better Model Design
43. DRY is about Knowledge | Mathias Verraes DRY + Domain-Driven Design 1. Better Model Design
44. 2. Refactoring God Object 1. Better Model Design
45. Go with clear business merit with incremental release Don’t underestimate, It takes time!!
46. Example: complex Order model Order status: new / ordered / paid / fulfilled / shipping / finished Order cannot track multiple Shipments Mixing Domains: Process / Payment / Fulfillment / Shipment Changing Order needs re-Payment Order Shipment Shipment Shipment Basket Payment Order Related Order needs another Order etc….
48. Is your Software Ready for the Next Build? – Webomates
49. Order status: new / ordered / paid / fulfilled / shipping / finished Shipment Shipment Shipment Order status: new / ordered / paid / fulfilled Track multiple Shipments No need to re-payment Make multiple Orders Order Shipment Shipment Shipment Basket Payment Order Shipment Shipment Shipment Order status: paid / fulfilled Basket Order status: paid / fulfilled 2. Refactoring God Object
50. Refactoring Legacy Code with the Strangler Fig Pattern - Shopify
51. Is the monolith a problem? No The problem is often “God Object” there is a tendency to blame the technology the issue of modeling
52. To fix “God Object” 2. Refactoring: Incremental release with business merit 1. North star modeling: understanding DRY + DDD Feature Flag (Canary release) Shadow Traffic (Parallel adoption) Strangler Fig (Phased implementation)
53. Thank you! Let’s have a chat! https://chikahirotokoro.com Chikahiro Tokoro https://en.kaigaiiju.ch Interview to Matz! with AI translation