Scaling Fast with Confidence: Evolving NEWT’s Backend Code Architecture

At ReiwaTravel, we’re evolving NEWT’s backend code architecture to enable more independent teams, reduce complexity, and move faster. In this presentation, I’ll share how we’re structuring our TypeScript monorepo with clear layers, modular boundaries, and architectural patterns that improve maintainability, reduce conflicts, and support long-term scalability—even as the team grows and features multiply.

Transcript

1. © 2023 Reiwa Travel, Inc.
 Scaling Fast with Confidence Evolving NEWT’s Backend Code Architecture
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. シリーズAラウンドにて48億円の資⾦調達を実施 Series A funding round テクノロジー分野への投資を加速し、グローバル展開へ。シリーズAの資⾦調達により、さらに⼤胆に技術 投資を⾏い、最先端テクノロジーを活⽤し、デバイスに最適化した最⾼のユーザビリティーの実現、個⼈ に合わせた情報提供など、これまでの旅のスタイルを根底から変えていく挑戦を加速。さらに、今後、国 内旅⾏事業、フライト予約機能、グローバル展開と事業ポートフォリオを拡⼤予定。
6. 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
7. 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。
8. 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。
10. 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
11. 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
12. 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
13. 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!
14. © 2023 Reiwa Travel, Inc.
 Scaling Fast with Confidence Evolving NEWT’s Backend Code Architecture
15. AGENDA
 © 2023 Reiwa Travel, Inc.
 1. Context: How we started 2. Problem: What challenges we are facing 3. Action: What we are doing to solve them
16. CONFIDENTIAL
 © 2023 Reiwa Travel, Inc.
 Context How we started
17. NEWT Tech stack
18. NEWT Tech stack
19. NEWT Tech stack
20. NEWT Tech stack
21. NEWT Tech stack
22. Backend API We started as a Modular Monolith • We have some base rules about how to structure each module • We provided freedom to developers to quickly ship features ├ 📁modules │ ├ 📁module-A │ ├ 📁module-B │ └ 📁… └ 📄server.ts
23. Backend API We started as a Modular Monolith • We have some base rules about how to structure each module • We provided freedom to developers to quickly ship features ├ 📁modules │ ├ 📁module-A │ ├ 📁module-B │ └ 📁… └ 📄server.ts The first years everything was good, until we start growing in products, team members, users… ⚠
24. CONFIDENTIAL
 © 2023 Reiwa Travel, Inc.
 Problem What challenges we are facing
25. © 2023 Reiwa Travel, Inc.
 Challenge ① Multiple Products
26. Challenge ① : Multiple Products We scaled from one product to multiple products
27. Challenge ① : Multiple Products New Products Development, needed to share existing code, so we just treated them as a module, since at the beginning, new products were PoCs, min investment to deliver
28. Challenge ① : Multiple Products During PoC was ok, but more and more features were needed, and these Product modules started to be big
29. Challenge ① : Multiple Products During PoC was ok, but more and more features were needed, and these Product modules started to be big
30. © 2023 Reiwa Travel, Inc.
 Challenge ② Multiple Backend Teams
31. We scaled from one backend team to multiple backend teams per product Challenge ② : Multiple Backend Teams
32. Challenge ② : Multiple Backend Teams Even separating members in teams for each product, the code was not allowing this isolation & flexibility
33. Modules were depending heavily on each other Challenge ② : Multiple Backend Teams
34. Modules were depending heavily on each other Challenge ② : Multiple Backend Teams
35. A small change in one module affects others and Increased risk of breaking unrelated parts of the system. Challenge ② : Multiple Backend Teams
36. Cycle Dependencies Challenge ② : Multiple Backend Teams
37. Cycle Dependencies Challenge ② : Multiple Backend Teams
38. These challenges can be summarized in the following issues • Dependency issues ◦ Modules depending heavily on each other ◦ A small change in one module affects others ◦ Increased risk of breaking unrelated parts of the system • Code Complexity ◦ Code that is difficult to understand or navigate ◦ Developers need to know too much before making a change ◦ Hard to onboard new members ◦ Debugging and maintenance take longer Summary
39. © 2023 Reiwa Travel, Inc.
 🧠 The turning point How can we scale faster and with confidence?
40. Context • We need to make NEWT Global and expand what each product can do • We need to increase the backend team members to achieve this 🧠 The turning point
41. Our Goals • Create isolated teams • Reduce the complexity of our system/code • Allow engineers to make changes with confidence • Onboard new members faster • Prepare our code to scale 🧠 The turning point
42. CONFIDENTIAL
 © 2023 Reiwa Travel, Inc.
 Actions What we are doing to solve them
43. © 2023 Reiwa Travel, Inc.
 Action ① We moved from Modular Monolith to Modular Monolith Monorepo
44. To support the scale of products, teams and maximize the reutilization of our current logic We moved from Modular Monolith to Modular Monolith Monorepo Action ①：Modular Monolith Monorepo
45. 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 Action ①：Modular Monolith Monorepo
46. 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 Action ①：Modular Monolith Monorepo
47. © 2023 Reiwa Travel, Inc.
 Action ② To control Dependencies issues, we introduced a Shared Layer & Service Contracts
48. • Files inside the shared layer can be imported from outside modules • We have a public Service class (Facade) that provide functionality with a easy to understand interface (contract) hiding complexity Action ②：Shared Layer
49. Communication flow using the shared layer Action ②：Shared Layer
50. If NEWT Tour team, need a functionality from NEWT Hotel team, that functionality need to be exposed in the shared layer Action ②：Shared Layer
51. Application Request Flow, also becomes simpler Action ②：Shared Layer
52. © 2023 Reiwa Travel, Inc.
 Action ③ To reduce Code Complexity We introduced Clear Layers + Coding Rules
53. We introduced Clear Layers Action ③：Clear Layer + Coding Rules
54. We introduced Clear Layers Action ③：Clear Layer + Coding Rules
55. ⚠ About Rules! • Too many rules and structure can increase complexity • While implementing we discussed with team members to simplify layers, process • We agreed which parts of the system we wanted to protect and provide flexibility in other areas • Linters warning us about wrong usage • We used AI Agents rules to generate most of the code Action ③：Clear Layer + Coding Rules
56. © 2023 Reiwa Travel, Inc.
 Summary Of Actions
57. • We moved from Modular Monolith to Modular Monolith Monorepo • Each product area became an isolated context (Packages) • To reduce dependencies issues, we introduced a Shared Layer • To reduce code complexity we introduced Clear Layers and Coding Rules Summary of changes
58. © 2023 Reiwa Travel, Inc.
 振り返り
59. • 🧩 Don’t over-engineer early, but invest in structure before it hurts ◦ Refactoring code takes time, make decisions that helps to reduce this pain • 🥷 Build your system for all engineers ◦ Do not depend on specific individuals, all members should be able to make changes with confidence to any part of the system • 🤖 The future is AI-assisted, structure is your best investment ◦ Allow engineers to focus in what is important 振り返り
60. Thank you!
 © 2023 Reiwa Travel, Inc.
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