Introduction

This post provides a comprehensive list of common interview questions for Meta’s Software Engineer - OS Frameworks in-domain system design interview. Use this as a quick reference guide for interview preparation and practice.

Note: These questions are organized by category. For detailed preparation strategies, see the Meta OS Frameworks Interview Preparation Checklist.

Common Meta OS Frameworks Design Questions

Android Framework Design Questions

These questions focus on designing Android framework components and services.

1. Design an Android Framework Service

Key Areas:

  • Design a system service for Android (e.g., Location Service, Notification Service)
  • Inter-process communication using Binder
  • Lifecycle management
  • Resource management (memory, CPU, battery)
  • Permission and security model

Example Services:

  • Location Service
  • Notification Service
  • Sensor Service
  • Camera Service
  • Audio Service
  • Window Manager Service

2. Design a Background Task Scheduling System

Key Areas:

  • Schedule and execute background tasks
  • Handle task priorities and constraints
  • Battery optimization considerations
  • Work scheduling across different Android versions
  • Task persistence and recovery

Considerations:

  • JobScheduler API
  • WorkManager
  • AlarmManager
  • Battery optimization (Doze mode, App Standby)
  • Foreground vs. background tasks

3. Design a Memory Management Framework

Key Areas:

  • Heap allocation and deallocation
  • Memory pool management
  • Garbage collection coordination
  • Memory leak detection and prevention
  • Low memory handling and OOM prevention

Considerations:

  • ART/Dalvik heap management
  • Memory limits per process
  • Low Memory Killer (LMK)
  • Memory profiling
  • Reference management

4. Design an IPC (Inter-Process Communication) System

Key Areas:

  • Design a communication mechanism between processes
  • Binder vs. other IPC mechanisms
  • Serialization/deserialization
  • Security and permission enforcement
  • Performance optimization

IPC Mechanisms:

  • Binder (Android’s primary IPC)
  • Shared memory (Ashmem)
  • Message queues
  • Sockets
  • Pipes

5. Design a Notification System Framework

Key Areas:

  • Display notifications to users
  • Notification channels and priorities
  • Battery and resource optimization
  • Notification grouping and management
  • Cross-app notification coordination

Considerations:

  • Notification channels
  • Notification priorities
  • Notification grouping
  • Heads-up notifications
  • Notification actions
  • Battery impact

6. Design a Location Services Framework

Key Areas:

  • GPS and network-based location
  • Location updates and callbacks
  • Battery optimization strategies
  • Privacy and permission handling
  • Location caching and accuracy

Location Sources:

  • GPS (high accuracy, high power)
  • Network (WiFi, cell towers)
  • Fused location provider
  • Passive location

Native/Kernel Integration Questions

These questions focus on bridging between Java and native code, and kernel-level components.

7. Design a JNI (Java Native Interface) Bridge

Key Areas:

  • Efficient data transfer between Java and native code
  • Memory management across boundaries
  • Error handling and exception propagation
  • Performance optimization
  • Thread safety considerations

See Also: Detailed JNI Bridge Design Guide

Critical Topics:

  • Reference management (local, global, weak)
  • Data type mapping
  • Method ID caching
  • Direct buffer usage
  • Exception handling

8. Design a Device Driver Interface

Key Areas:

  • Hardware abstraction layer (HAL)
  • Driver registration and discovery
  • Device file system interface
  • Error handling and recovery
  • Multi-device support

Driver Types:

  • Character devices
  • Block devices
  • Network devices
  • Android-specific drivers (Binder, Ashmem)

9. Design a Kernel Module System

Key Areas:

  • Loadable kernel modules
  • Module dependencies
  • Module lifecycle management
  • Security and isolation
  • Performance monitoring

Considerations:

  • Module loading/unloading
  • Module dependencies
  • Kernel version compatibility
  • Security policies
  • Module initialization

10. Design a System Call Interface

Key Areas:

  • User-space to kernel-space communication
  • System call registration and routing
  • Parameter validation and security
  • Performance optimization
  • Backward compatibility

Considerations:

  • System call numbers
  • Parameter marshalling
  • Security checks
  • Error handling
  • Performance overhead

OS-Level Resource Management Questions

These questions focus on managing system resources like processes, memory, I/O, and power.

11. Design a Process/Thread Management System

Key Areas:

  • Process creation and termination
  • Thread pool management
  • Priority scheduling
  • CPU affinity and load balancing
  • Resource limits and quotas

Considerations:

  • Process lifecycle
  • Thread scheduling
  • Priority levels
  • CPU affinity
  • Resource quotas

12. Design a File System Interface

Key Areas:

  • File operations (read, write, delete)
  • File system abstraction
  • Caching and buffering strategies
  • Permission management
  • Performance optimization

File Systems:

  • ext4 (Android default)
  • F2FS (Flash-Friendly File System)
  • Virtual file systems
  • Storage abstraction

13. Design a Network Stack Interface

Key Areas:

  • Socket abstraction
  • Network protocol handling
  • Connection management
  • Bandwidth management
  • Security and encryption

Considerations:

  • TCP/UDP sockets
  • Network protocols
  • Connection pooling
  • Bandwidth throttling
  • TLS/SSL support

14. Design a Power Management System

Key Areas:

  • CPU frequency scaling
  • Device state management (sleep, wake)
  • Battery monitoring
  • Power optimization strategies
  • Wake lock management

Power States:

  • Active
  • Idle
  • Sleep
  • Deep sleep
  • Wake locks

Framework Architecture Questions

These questions focus on framework design patterns and architectural components.

15. Design a Plugin/Extension Framework

Key Areas:

  • Dynamic plugin loading
  • Plugin isolation and security
  • Plugin dependencies
  • Lifecycle management
  • Version compatibility

Considerations:

  • Plugin discovery
  • Plugin loading mechanisms
  • Security sandboxing
  • Plugin lifecycle
  • API versioning

16. Design a Configuration Management System

Key Areas:

  • System-wide configuration
  • Configuration persistence
  • Dynamic configuration updates
  • Configuration validation
  • Rollback mechanisms

Configuration Types:

  • System properties
  • Build configuration
  • Runtime configuration
  • User preferences
  • Feature flags

17. Design a Logging and Debugging Framework

Key Areas:

  • Centralized logging system
  • Log levels and filtering
  • Performance impact minimization
  • Log rotation and retention
  • Debugging tools integration

Logging Components:

  • Logcat
  • Log levels (VERBOSE, DEBUG, INFO, WARN, ERROR)
  • Log rotation
  • Log filtering
  • Performance impact

18. Design a Security Framework

Key Areas:

  • Permission system
  • Sandboxing and isolation
  • Secure storage
  • Cryptographic operations
  • Security policy enforcement

Security Components:

  • Android permissions
  • SELinux policies
  • App sandboxing
  • KeyStore
  • Security policies

Performance and Optimization Questions

These questions focus on performance monitoring, profiling, and optimization.

19. Design a Performance Profiling System

Key Areas:

  • CPU profiling
  • Memory profiling
  • I/O profiling
  • Real-time performance monitoring
  • Performance data collection and analysis

Profiling Tools:

  • Systrace
  • Perfetto
  • CPU profilers
  • Memory profilers
  • I/O profilers

20. Design a Caching Framework

Key Areas:

  • Multi-level caching (L1, L2, L3)
  • Cache eviction strategies
  • Cache consistency
  • Memory-efficient caching
  • Performance optimization

Cache Types:

  • Memory cache
  • Disk cache
  • Network cache
  • Application cache
  • System cache

Integration and Compatibility Questions

These questions focus on cross-platform support, compatibility, and build systems.

21. Design a Backward Compatibility Layer

Key Areas:

  • API versioning
  • Legacy API support
  • Migration strategies
  • Compatibility testing
  • Performance overhead minimization

Considerations:

  • API levels
  • Feature flags
  • Deprecation strategies
  • Compatibility libraries
  • Performance impact

22. Design a Multi-Platform Abstraction Layer

Key Areas:

  • Platform-specific code abstraction
  • Cross-platform APIs
  • Platform feature detection
  • Conditional compilation strategies
  • Performance optimization per platform

Platforms:

  • Android (ARM, x86)
  • Different Android versions
  • Different hardware configurations
  • Different form factors (phone, tablet, TV)

23. Design a Build System Integration

Key Areas:

  • Build system integration
  • Dependency management
  • Incremental builds
  • Cross-compilation support
  • Build optimization

Build Systems:

  • Gradle
  • Android.mk
  • CMake
  • Soong (Android build system)
  • Bazel

Question Categories by Frequency

Most Common Questions (Priority 1)

These questions appear most frequently in Meta OS Frameworks interviews:

  1. Design an Android Framework Service (#1)
  2. Design a JNI Bridge (#7)
  3. Design a Background Task Scheduling System (#2)
  4. Design an IPC System (#4)
  5. Design a Memory Management Framework (#3)

Common Questions (Priority 2)

These questions appear regularly:

  1. Design a Location Services Framework (#6)
  2. Design a Process/Thread Management System (#11)
  3. Design a Power Management System (#14)
  4. Design a Security Framework (#18)
  5. Design a Device Driver Interface (#8)

Less Common but Important (Priority 3)

These questions may appear but are less frequent:

  1. Design a Notification System Framework (#5)
  2. Design a File System Interface (#12)
  3. Design a Network Stack Interface (#13)
  4. Design a Plugin/Extension Framework (#15)
  5. Design a Performance Profiling System (#19)

How to Use This List

Preparation Strategy

  1. Start with Priority 1 Questions
    • Focus on the most common questions first
    • Practice with detailed solutions
    • Understand all key concepts
  2. Move to Priority 2 Questions
    • Cover common but less frequent questions
    • Practice problem exploration
    • Understand trade-offs
  3. Review Priority 3 Questions
    • Familiarize yourself with concepts
    • Understand basic approaches
    • Know when to apply them

Practice Approach

For each question, practice:

  1. Problem Exploration
    • Ask clarifying questions
    • Gather requirements
    • Understand constraints
  2. Design Approach
    • High-level architecture
    • Component design
    • Data structures
  3. Resource Management
    • Memory management
    • CPU usage
    • Battery optimization
  4. Trade-offs
    • Performance vs. battery
    • Accuracy vs. power
    • Simplicity vs. flexibility
  5. Deep Dive
    • Detailed implementation
    • Code examples
    • Edge cases
  6. Quantitative Analysis
    • Calculations
    • Estimates
    • Performance metrics

Interview Tips

  1. Don’t Memorize Solutions
    • Focus on understanding concepts
    • Practice problem-solving approach
    • Show your thought process
  2. Ask Questions
    • Clarify requirements
    • Understand constraints
    • Gather context
  3. Think Out Loud
    • Explain your reasoning
    • Discuss alternatives
    • Show your analysis
  4. Consider Trade-offs
    • Always discuss pros and cons
    • Make informed decisions
    • Explain your choices
  5. Be Flexible
    • Adjust based on feedback
    • Consider different approaches
    • Show adaptability

Conclusion

This list provides a comprehensive overview of common Meta OS Frameworks interview questions. Remember:

  • Focus on understanding concepts, not memorizing solutions
  • Practice problem-solving approach, not specific answers
  • Show your thought process, communicate clearly
  • Consider trade-offs, make informed decisions
  • Be prepared for follow-ups, dive deeper when asked

Good luck with your interview preparation!