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Stage 5 · System design

Mobile System Design blueprint

Twenty architecture decisions every mobile system meets, each built around one worked failure case, with a rubric to review them.

5.0 · 1 review on Gumroad

About the book

Mobile system design is not a collection of diagrams. It is the work of making decisions while requirements, traffic, teams and platform constraints keep moving.

This book puts you inside realistic iOS and Android scenarios and asks you to frame the problem, choose the tradeoffs, migrate safely, operate the result and preserve a way back.

Each chapter is a working laboratory with a decision record, exercises, field guidance and an answer key, so you practice judgment instead of memorizing architecture vocabulary.

What you get

  • 20 decision chapters, each around one worked failure case
  • 12 longitudinal scenarios, from payments to an AI assistant, each across five stages with an incident
  • 50 scored decision exercises with a complete answer key
  • The Blueprint rubric (7 dimensions, 0 to 28) and five more named frameworks
  • Complete and Master add dark editions, templates, a Swift and Kotlin companion (7 modules) and a toolkit

A page from the book

Copied as printed, so you can judge the format before you buy.

The Blueprint frameworks, page 473

Worked mini-example: scoring a design with the rubric

A team proposes moving conflict resolution for offline notes from last-write-wins to a conflict-free replicated data type. Problem and invariants: 3 (invariant “no user edit is silently lost” is stated). State and authority: 4 (server is the merge authority, clients propose operations, written clearly). Compatibility and evolution: 1 (nothing said about notes created by old clients that still send last-write-wins). Reliability and operations: 2 (rollback exists but no metric detects silent data loss). Security and privacy: 3. Organization and adoption: 3. Evidence and learning: 2. Total 18 of 28. The low compatibility score is the headline: the design is sound in steady state but has no story for the migration window, which is exactly where notes will be lost. The review now has a target.

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What is inside

  1. 1The architecture decision loopp. 9
  2. 2Requirements as invariants, budgets, and failure policyp. 23
  3. 3Client-server boundaries and authorityp. 37
  4. 4State ownership and canonical sources of truthp. 50
  5. 5Offline-first beyond cachingp. 63
  6. 6Synchronization, consistency, and conflict policyp. 76
  7. 7Idempotency, retries, and persistent state machinesp. 89
  8. 8Version skew and backward compatibilityp. 102
  9. 9Schema and data migrationsp. 116
  10. 10Background work and process restorationp. 129
  11. 11Performance, battery, memory, and thermal budgetsp. 144
  12. 12Security, identity, attestation, and privacy boundariesp. 157
  13. 13Mobile observability and reliability metricsp. 172
  14. 14Release trains, progressive rollout, flags, and kill switchesp. 186
  15. 15Incident response when the client cannot be patched immediatelyp. 199
  16. 16Modularization, build systems, and CI economicsp. 213
  17. 17Shared foundations, SDK design, and developer experiencep. 228
  18. 18Platform teams, governance, RFCs, and architecture fitnessp. 241
  19. 19Cross-platform ownership boundaries and migration economicsp. 255
  20. 20On-device and hybrid AI as a versioned systemp. 268

What readers say

  • “great book, it’s exactly what we need in 2026, and it’s exactly as advertised”

    Marcus Ar.
    Gumroad verified purchase

Reader reviews from Gumroad, word for word.

Who this is for

This is for you ifYou need a repeatable way to make and defend mobile architecture decisions.

  • Senior Engineer
  • Staff candidate
  • Aspiring Mobile Architect
  • Tech Lead
The library pathWhere this fits
  1. 01Get foundThe Silent Rejection
  2. 02Build the record and negotiateThe iOS Engineer Playbook · Leverage
  3. 03InterviewThe iOS interview blueprint · The senior signal · Top 300 React Native interview questions · 500 Flutter interview questions · The senior SDET interview handbook
  4. 04Answer practice and live roundsThe 24-hour iOS interview answer book · The 24-hour Android interview answer book · Share your screen
  5. 05Architecture and qualitySwiftUI under load · Mobile System Design blueprint · Security is a feature · The Second PassYou are here
  6. 06Staff systems and ownershipAltitude · Ticket taker, outcome owner
  7. 07Build with AIBuild with your brain on (coming soon)
  8. 08LeadLeadership blueprint (coming soon)
  9. 09ArchitectArchitect blueprint (coming soon)
Portrait of Mike Salari

About the author

Mike Salari

Staff mobile engineer · 500+ technical interviews from the hiring side.

I wrote this from mobile architecture work in fintech and regulated domains where correctness, security and maintainability are not optional.

15 years building production mobile software, with experience across Apple, Adobe, Cisco, Mastercard and Visa.

Read the full story

Before or after you buy

Free guide

Mobile system design interview preparation

Prepare mobile system design interviews with a framework for offline data, synchronization, caching, performance, security and rollout.

Free guide

Offline-first mobile architecture

Design offline-first mobile apps with a local source of truth, pending writes, conflict handling, sync state and honest UX.

Free guide

Mobile data synchronization design

Design reliable mobile data synchronization with idempotency, conflict handling, retries, ordering and observable sync state.

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