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Altitude: the missing bridge between senior mobile engineer and staff engineer

How complete systems are designed, reviewed and run around the app: backend, security, reliability and production tradeoffs.

5.0 · 1 reader review

About the book

Altitude is a field guide to staff-level mobile systems engineering for senior mobile engineers, staff engineers, mobile architects and technical leads.

It connects mobile architecture, backend contracts, security, observability, offline sync, distributed systems, cloud, incidents and architecture reviews into one way of reasoning about the whole system.

What you get

  • Systems thinking, and the mobile client as a node in a distributed system
  • Mobile system design, modularisation, server-driven UI and performance as system properties
  • API design, backend for frontend, versioning, caching, offline-first and sync with conflict resolution
  • Authentication with OAuth2, OIDC and JWT, threat modelling, observability and incidents
  • Three end-to-end case studies: ride hailing, global messaging and a high-assurance financial platform
  • Every chapter: exercises from warm-up to stretch and a hostile review, interview questions with what a strong answer covers, and full answers in the companion

A page from the book

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

Chapter 22, refresh rotation, reuse detection, and the train problem

Refresh rotation, reuse detection, and the train problem

Turning on a refresh token is not enough. A refresh token that never rotates and never expires is a finding in any modern security review, because a single leaked one becomes permanent account access with no detection signal. The fix is rotation: every time the client redeems a refresh token, the server issues a new refresh token and invalidates the old one. Now a leaked token is only useful until the legitimate client refreshes next, and you get a detection signal for free.

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Before and after

Architecture review

Before

This module should talk to the API directly.

After

I would define the client contract, failure modes, rollout plan and observability first.

Then I would decide whether direct API access, a BFF or a sync layer owns the responsibility.

Staff-level system design answer

Before

The app caches data and retries requests.

After

The app is a distributed node with local state, partial connectivity and lifecycle interruptions.

I would design freshness, idempotency, conflict handling, telemetry and backward compatibility together.

Learn through complete systems, not toy examples.

Three end-to-end architectures, each worked through the way a staff engineer reasons about a real product: the design, the trade-offs, the failure modes and the decisions.

Inspired by Uber

Ride-hailing platform

  • Dispatch and matching
  • Realtime tracking
  • Event-driven architecture
  • Offline behaviour
  • Observability
  • Production failures

Inspired by WhatsApp

Global messaging

  • Message delivery
  • Realtime communication
  • Synchronization
  • Multi-device consistency
  • Offline support
  • Encryption architecture

Inspired by Revolut

High-assurance fintech

  • Authentication and device trust
  • Authorisation
  • Fraud detection
  • Risk engines
  • Security architecture
  • Compliance

What is inside

  1. 1From feature owner to systems thinkerp. 1
  2. 2The mobile client as a distributed-systems nodep. 11
  3. 3How to read an architecturep. 22
  4. 4The mobile system design frameworkp. 33
  5. 5Domain boundaries for mobile systemsp. 48
  6. 6Modular and feature-based architecture for multi-team codebasesp. 66
  7. 7Server-driven UI and the build-versus-ship-versus-configure decisionp. 80
  8. 8Super apps, mini-app runtimes, and platform engineeringp. 91
  9. 9Performance engineering, startup, frames, memory, and battery as system propertiesp. 103
  10. 10Mobile architecture governance and team topologiesp. 120
  11. 11API design for mobile, REST, GraphQL, and the cost of chattinessp. 142
  12. 12Backend for frontend, patterns, ownership, anti-patternsp. 155
  13. 13API evolution, versioning, and never breaking the old appp. 169
  14. 14Offline-friendly API designp. 187
  15. 15Caching and cache invalidation without lying to the userp. 202
  16. 16Offline-first and local-first architecturep. 215
  17. 17Sync engines and conflict resolutionp. 234
  18. 18Distributed systems fundamentalsp. 250
  19. 19Resilience patterns on the clientp. 270
  20. 20Event-driven systems and what they mean for the clientp. 294
  21. 21Real-time delivery, push, WebSockets, SSE, and catch-up after offlinep. 310
  22. 22Authentication and authorisation done right on mobilep. 324
  23. 23Mobile security, privacy and threat modelling, from OWASP to attestation, bot defense and the data lifecyclep. 342
  24. 24Observability for mobile, telemetry you cannot hotfixp. 371
  25. 25The mobile delivery system, from commit to safe adoptionp. 393
  26. 26Cloud and Kubernetes for mobile architects, the mental model, not the manifestsp. 411
  27. 27Becoming the staff mobile engineerp. 426
  28. 28Case study, a ride-hailing platformp. 438
  29. 29Case study, a global messaging platformp. 466
  30. 30Case study, a high-assurance financial platformp. 496
  31. Glossaryp. 529

The Engineering Companion

The purchase includes the Altitude Engineering Companion: four PDF volumes, 410 pages. It is practice material for after the chapters. It references the book by chapter and section, and it assumes the book is open beside it.

In all: 30 chapter-aligned worksheets, 6 game-day exercises, 3 capstone challenges with worked solutions, 16 practical engineering templates, 5 completed examples, 6 checklists, and review notes for all 30 worksheets.

  1. 01Engineering Companion Guide. Where to start. A map from each chapter to its exercises, and the capstone challenges that each combine several chapters into one design.
  2. 02Architecture and System Design Workbook. The chapter-aligned worksheets. Each sets an objective, a scenario, constraints, deliverables and evaluation criteria.
  3. 03Staff Engineering Field Kit. The review templates, completed examples and checklists, each tied to the chapters that justify it.
  4. 04Worked Solutions and Review Notes. Review notes for every worksheet, and one defensible answer for each capstone.

What readers say

  • “this book was the gap I didn't even know I had.,, and is the reason I came back and bought Mike's other books. No motivational b***s***, just practical insights that made a lot of things click for me. A f***ing great read. I recommended.”

    Nick R.
    Gumroad verified purchase

Reader reviews from Gumroad. Review text preserved, with punctuation normalized to the site style.

Who this is for

This is for you ifyou are delivering senior work, but your scope does not yet change what other teams can do.

  • Senior iOS engineers
  • Senior Android engineers
  • Mobile architects
  • Technical leads
  • Staff engineer candidates

Not for

  • Beginners learning mobile fundamentals
  • Framework tutorials or UI implementation patterns
  • LeetCode-only interview preparation
  • Anyone looking for shallow interview answers
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 · The Flutter Interview Book · 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 Pass
  6. 06Staff systems and ownershipAltitude · Ticket Taker, Outcome OwnerYou are here
  7. 07Build with AIBuild With Your Brain On (coming soon) · Engineering Software with Coding Agents
  8. 08LeadBefore the Room
  9. 09ArchitectControlled Change
Portrait of Mike Salari

About the author

Mike Salari

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

I wrote Altitude for mobile engineers who need to operate beyond the app surface: across APIs, security, observability, resilience, cloud, production incidents and technical leadership.

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

Read the full story

Before or after you buy

FAQ

Altitude: questions before you buy

What is Altitude?

Altitude is a field guide to staff-level mobile systems engineering, focused on architecture, distributed systems, security, observability, system design and technical leadership.

Who should read Altitude?

Senior iOS engineers, senior Android engineers, mobile architects, technical leads and engineers preparing for staff-level responsibilities.

Is Altitude an interview preparation book?

No. It focuses on real-world systems engineering rather than memorising interview answers, though the systems thinking it builds helps in senior and staff interviews.

Does Altitude cover system design?

Yes. Mobile system design, distributed systems, architecture trade-offs, scalability and reliability are core themes.

Does Altitude cover BFF (Backend-for-Frontend) architecture?

Yes. It covers Backend-for-Frontend patterns, API orchestration, aggregation and mobile-specific backend design in depth.

Does Altitude cover OAuth, OIDC and JWT?

Yes. Modern authentication, authorisation, token handling and security architecture are included.

Does Altitude cover distributed systems?

Yes. Event-driven systems, consistency models, messaging, caching, synchronisation and reliability concepts are explained from a mobile engineer's perspective.

Does Altitude cover Kubernetes and cloud concepts?

Yes. The book covers Kubernetes fundamentals and cloud concepts relevant to software architects and staff engineers.

Does Altitude cover observability and production reliability?

Yes. Telemetry, monitoring, SLOs, incident response and turning production failures into better systems are central to the book.

Is Altitude useful for iOS engineers?

Yes. Most of it is written from the mobile side, and the architecture material applies to broader software work.

Is Altitude useful for Android engineers?

Yes. The systems thinking, architecture and security material is platform-agnostic, and the examples translate directly to Android.

Does Altitude contain real-world case studies?

Yes. The book includes detailed architecture studies inspired by ride-hailing, messaging and fintech platforms.

Is Altitude only about mobile?

No. It is written from a mobile engineering perspective but connects the app to backend contracts, security, distributed systems and cloud, the full system around it.

How many years of experience should I have?

The material is most valuable for engineers with several years of professional experience who are moving toward architecture and staff-level work.

What format is Altitude, and how do I get it?

Altitude is an instant PDF and EPUB download through Gumroad. The purchase also includes the Engineering Companion, four PDF volumes with 410 pages, and updates to the second edition.

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