NEWT Backend Evolution

Rodrigo Ramirez

July 14, 2025

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1. © 2023 Reiwa Travel, Inc.
 Scaling Fast with Confidence NEWT

   Backend Evolution

2. © 2023 Reiwa Travel, Inc.
 Profile • Nationality: Argentinian •

   Language: Spanish, English, Japanese • Full Stack Developer (+10y) Career • 󰎆 2006~: Freelance • 󰎆 2008~: PowerSite ( CTO/CEO ) ◦ Email Marketing SaaS • 󰏦 2015~: Travelience ( CTO ) ◦ Tour Guide Marketplace • 󰏦 2021~: ReiwaTravel ( Senior Engineer ) Senior Engineer / Product-Dev Rodrigo Ramirez

3. 令和トラベル‧NEWTについて Information 1.

4. 社名 株式会社令和トラベル 代表者 篠塚 孝哉 創業 2021年4⽉5⽇ 従業員 100名（役員‧正社員）※2024年5⽉1⽇時点 登録番号

   観光庁⻑官登録旅⾏業第2123号 資本⾦ 70.2億円 (資本剰余⾦を含む） 会社概要 About Us

5. あたらしい旅⾏を、デザインする。 私たちは旅⾏が⼈⽣を豊かにしてくれると信じている。デジタルの⼒を活⽤し、 よりあたらしい旅⾏体験へとアップデートしていくことが、私たちの使命であり挑戦である。 ミッション Mission

6. 事業⽅針‧計画 Our Business Plan ツアーから始まり、ホテル、エアー、グループ旅⾏と事業ポートフォリオを拡⼤予定。 テクノロジーを活⽤し、すべての旅⾏に対応するデジタルトラベルエージェンシーを⽬指しています。

7. 事業⽅針‧計画 Our Business Plan 事業ポートフォリオの拡⼤と並⾏し、マーケットのターゲットを広げることで、事業の規模を伸ばしていきます。

8. None

9. 私たちのサービス Our Service 海外ツアー予約 宿‧ホテル予約 (ホテル + 航空券セット) 旅⾏ ガイド

   トラベル コンシェルジュ グループトラベル ‧修学旅⾏  ‧企業の研修旅⾏など かんたん‧おトク‧えらべる‧あんしんな旅⾏の提供 ‧旅⾏相談 ‧VIP対応

10. 海外ツアー予約 Overseas Tour Reservations ⼤⼿ECサイトでミネラルウォーターを買うくらい「かんたん」に海外旅⾏を予約 煩雑になりがちな海外旅⾏予約を、直感的なUI/UXでストレスフリーなサービス設計

11. 海外ツアー予約 Overseas Tour Reservations 予約のスマート管理 旅程表やチケットはすべてアプリに やることリスト 出発前の準備もばっちり パスポートスキャン トラベルリンク

    同⾏者のアプリに予約をリンク 煩雑な旅⾏準備もアプリで完結 パスポートはカメラで読みとり

12. ⼀緒にチャレンジしてくれる仲間を募集中！ We Want Co-Workers Who Will Take on A Challenge

    with Us!

13. © 2023 Reiwa Travel, Inc.
 Scaling Fast with Confidence NEWT

    Backend Evolution

14. AGENDA
 © 2023 Reiwa Travel, Inc.
 1. Context 2. Challenges

    3. 振り返り

15. CONFIDENTIAL
 © 2023 Reiwa Travel, Inc.
 Context NEWT Overview

16. NEWT Tech stack

17. NEWT Tech stack

18. Backend Stack 📆 Tech choices made in 2021 (PoC start

    – now ~4 years) • Language: TypeScript: ( Full-Stack team ) • Framework: None ( Build on top of Apollo Server and Express ) • ORM: TypeORM • Architecture: Modular Monolith • Infrastructure: GCP ├ 📁modules │ ├ 📁module-A │ ├ 📁module-B │ └ 📁… └ 📄server.ts

19. We scaled from one product to multiple products Business Evolution

20. We scaled from one backend team to multiple backend teams

    per product Team Evolution

21. CONFIDENTIAL
 © 2023 Reiwa Travel, Inc.
 Challenges What challenges do

    we have and how are we solving them?

22. © 2023 Reiwa Travel, Inc.
 Challenge ① 📦 Library Dependency

    Risks

23. Issue • TypeScript ecosystem moves quickly → upgrades and replacements

    are necessary • Core libraries used directly without abstraction layer → expensive technical debt Challenge ① : 📦 Library Dependency Risks

24. e.g: TypeORM • We decided to use TypeORM in 2021

    ( 4 years ago ) • Poor maintenance (project abandoned for long time) • Uncertainty about long-term evolution • Community migrating to Prisma Challenge ① : 📦 Library Dependency Risks

25. Migration Pains: • Entities are imported directly from module •

    Business logic mixed with ORM calls • Hard to replace Booking/User entity implementation • Tests must hit the database Challenge ① : 📦 Library Dependency Risks

26. Solution: • Added our Own repository layer to make swapping

    the ORM (TypeORM ↔ Prisma) easy • Testing simplified by mocking the repository interface • Incremental Replacement of current modules Challenge ① : 📦 Library Dependency Risks

27. Lesson learned: • Libraries can become outdated or stop being

    maintained • To reduce future migration pain, add an abstraction layer around any library you use deeply in your system Challenge ① : 📦 Library Dependency Risks

28. © 2023 Reiwa Travel, Inc.
 Challenge ② 🪄 Decorator Coupling

    Risks

29. Context • We used TypeGraphQL + TypeORM that works based

    on decorators Issue • Magic Behavior • Refactoring Challenges • Mixing decorators can cause issues and coupling Challenge ② : 🪄 Decorator Coupling Risks

30. Problems • GraphQL schema tied to entities • Cross-module cycles

    & tight coupling Challenge ② : 🪄 Decorator Coupling Risks

31. Solution • Separation of TypeORM & TypeGraphQL Challenge ② :

    🪄 Decorator Coupling Risks

32. © 2023 Reiwa Travel, Inc.
 Challenge ③ 🏢 Monolith Scalability

    Issues

33. Growth Pain • Modular Monolith → many products → many

    teams Issues • Products mixed inside monolith • No rules → no isolation • One change affects many modules • Single deploy → can’t split apps Challenge ③ : 🏢 Monolith Scalability Issues

34. Issue • Products mixed inside monolith Challenge ③ : 🏢

    Monolith Scalability Issues

35. Issue • No rules → no isolation Challenge ③ :

    🏢 Monolith Scalability Issues

36. Issue • No rules → no isolation Challenge ③ :

    🏢 Monolith Scalability Issues

37. Issue • Single deploy → can’t split apps Challenge ③

    : 🏢 Monolith Scalability Issues

38. Solution • Modular Monolith → Modular Monolith Monorepo Challenge ③

    : 🏢 Monolith Scalability Issues

39. We changed the directory structure to a typical TypeScript monorepo

    ├ 📁modules │ ├ 📁module-A │ ├ 📁module-B │ └ 📁… └ 📄server.ts ├ 📁apps │ ├ 📁app-A │ └ 📁app-B └ 📁packages ├ 📁package-A ├ 📁package-B └ 📁core Before After Challenge ③ : 🏢 Monolith Scalability Issues

40. Moved legacy code inside one of the apps and incrementally

    migrate it ├ 📁modules │ ├ 📁module-A │ ├ 📁module-B │ └ 📁… └ 📄server.ts ├ 📁apps │ ├ 📁app-A │ └ 📁app-B └ 📁packages ├ 📁package-A ├ 📁package-B └ 📁core Before After Challenge ③ : 🏢 Monolith Scalability Issues

41. • Turborepo for builds & parallel tasks • CODEOWNERS to

    assign ownership • ESLint rules block forbidden imports Challenge ③ : 🏢 Monolith Scalability Issues

42. © 2023 Reiwa Travel, Inc.
 Challenge ④ 🎨 Freedom &

    Governance

43. • Issue: TS has no single framework (unlike RoR/Laravel) ◦

    → Developers do as they like → more of the above problems • Need: Clear Structure + Coding Rules Challenge ④ : 🎨 Freedom & Governance

44. • Solution: ◦ Documentation as Code in .agent-rules/ ▪ AI

    agents read these rules automatically Challenge ④ : 🎨 Freedom & Governance

45. AI Code Agents can • Generate code by our standards

    • Migrate old code → new style • Answer architecture questions • Suggest improvements in code review Implementation • .agent-rules/ mirrors monorepo layout • GitHub Actions runs AI review jobs • Agents (Cursor, Cline, Claude) load rules Challenge ④ : 🎨 Freedom & Governance

46. © 2023 Reiwa Travel, Inc.
 振り返り

47. 🎯 Lessons Learned • Don’t over-engineer eraly, instead incrementally evolve

    your code before it hurts. • Correct usage of Code Isolation and Layers are important when growing • AI code agents are the future, clear rules helps us to fully use their potential 振り返り

48. Thank you!
 © 2023 Reiwa Travel, Inc.
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