AOSP

Boot

1. Walk through the complete Android boot sequence from power-on to system_server startup.

2. What is the role of the Boot ROM, and how does it verify the next stage bootloader?

3. Explain the differences between U-Boot, Little Kernel (LK), and proprietary bootloaders in AOSP.

4. How does avb_verify work in the context of Verified Boot 2.0 (AVB)?

5. What is the purpose of the boot.img header, and how do the V3 and V4 formats differ from V1/V2?

6. Describe the process of loading and verifying the vendor_boot partition.

7. How does the bootloader pass the kernel command line and device tree (DTB) to the Linux kernel?

8. What is the role of init in early userspace, and how does it parse init.rc scripts?

9. Explain the difference between early-init, init, and late-init stages in init.rc.

10. How does init handle the transition from the rootfs ramdisk to the system partition?

11. What is the purpose of the system/etc/init/ directory and how does it relate to first-stage vs second-stage init?

12. How do you debug early boot failures before logd and logcat are available?

13. Explain how dm-verity is initialized during boot and its impact on I/O performance.

14. What is the purpose of the vbmeta partition, and how are rollback indexes used?

15. How does the boot sequence differ between a normal boot and a recovery boot?

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Build

1. Explain the AOSP build system architecture: how do Soong, Kati, and Ninja interact?

2. What is the difference between Android.bp and Android.mk, and when would you still need the latter?

3. How does the Android.bp module system handle dependencies between shared libraries and static libraries?

4. Describe the purpose of AndroidProducts.mk, BoardConfig.mk, and device.mk in a device build.

5. How do you add a new HAL implementation to the build without modifying AOSP core repositories?

6. Explain the difference between eng, user, userdebug, and user build variants at the build system level.

7. What is the purpose of sepolicies in the build, and how are they compiled into the final image?

8. How does the build system generate OTA packages, and what is the role of releasetools.py?

9. Describe how to create a custom build target that packages additional prebuilt binaries.

10. What are apex modules, and how do they change the traditional system image partitioning?

11. How does the build system handle kernel compilation out-of-tree vs in-tree?

12. Explain the purpose of PRODUCT_COPY_FILES vs PRODUCT_PACKAGES and their build-time implications.

13. How do you implement a build-time flag that conditionally compiles source code across multiple modules?

14. What is the role of bionic in the build, and how does it differ from glibc-based builds?

15. How would you optimize a clean AOSP build time for a large team using distributed build caches?

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Framework

1. Explain the Zygote startup process and why it uses a prefork model.

2. What happens during ZygoteInit before the first application process is forked?

3. Describe the Binder IPC mechanism: how does a client obtain a reference to a system service?

4. What is the difference between BpBinder and BBinder, and how does the proxy/stub pattern work in native code?

5. How does AIDL differ from HIDL and AIDL (stable) in terms of interface stability and versioning?

6. Explain the role of ServiceManager vs hwservicemanager vs vndservicemanager.

7. What is the purpose of the system_server process, and how is it started from Zygote?

8. Describe the ActivityThread initialization sequence when an application process starts.

9. How does the PackageManagerService scan and resolve packages during boot?

10. Explain the difference between system permissions, signature permissions, and normal permissions in AndroidManifest.xml.

11. How does the WindowManagerService manage window layers and surface composition?

12. Describe the input event pipeline from kernel to application: EventHub, InputManagerService, InputDispatcher.

13. What is the role of SurfaceFlinger in the display pipeline, and how does it interact with HWC?

14. How does the PowerManagerService coordinate with the kernel for suspend/resume and wakelocks?

15. Explain the JobScheduler framework and how it interacts with Doze mode and App Standby.

16. What is the difference between a ContentProvider running in its own process vs the caller's process?

17. How does the ActivityManagerService handle process lifecycle and out-of-memory killing decisions?

18. Describe how BroadcastReceiver delivery works, including ordered vs unordered broadcasts and background restrictions.

19. What is the purpose of Looper, Handler, and MessageQueue in the Android threading model?

20. How does the Resources framework handle runtime resource overlay (RRO) and static overlay?

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System Service

1. How do you implement a new system service that is accessible to third-party applications?

2. What is the difference between a Java system service and a native system service in terms of registration?

3. Explain the SystemService base class and the onStart(), onBootPhase(), and onUserStarting() lifecycle methods.

4. How do you ensure thread safety in a system service that receives concurrent Binder calls?

5. Describe the watchdog mechanism (Watchdog.java) and how to register a system service with it.

6. How does ActivityManagerService enforce background execution limits introduced in recent Android versions?

7. Explain the architecture of ConnectivityService and how it manages multiple network agents.

8. How does LocationManagerService interact with GNSS HAL and fuse location providers?

9. Describe the power management flow from PowerManagerService to the kernel power HAL.

10. How does BatteryService monitor battery state and propagate events to the framework?

11. Explain the role of StorageManagerService and how it handles adopted storage vs portable storage.

12. How does AudioService manage audio focus, routing, and policy decisions across HAL implementations?

13. Describe the CameraService architecture and how it handles concurrent camera access from multiple apps.

14. What is the purpose of SensorService, and how does it batch sensor events for power efficiency?

15. How does TelephonyRegistry dispatch phone state changes to multiple listeners securely?

16. Explain the VibratorService and LightsService abstractions over their respective HALs.

17. How would you add a custom hardware feature (e.g., a proprietary sensor) and expose it through the framework?

18. Describe how DevicePolicyManagerService enforces enterprise policies at the system service level.

19. How does NetworkManagementService use netd to configure iptables and routing rules?

20. What is the role of AppOpsService and how does it provide fine-grained permission auditing beyond runtime permissions?