Design resource loader and ROS-like pub/sub

Q: Design resource loader and ROS-like pub/sub

This question evaluates system design and distributed-systems competencies including resource management, async concurrency, caching and eviction, streaming and partial loads, dependency resolution, failure isolation, observability, and pub/sub concerns such as topic/schema/versioning, discovery, QoS, ordering, replay, partitioning, latency, clock semantics, and security. Commonly asked to assess architectural reasoning about scalability, low-latency trade-offs, fault tolerance, and deployment/topology choices, it is categorized under System Design and tests both high-level conceptual understanding and practical application-level design decisions; English.

Q: How do I approach System Design interview questions?

System Design questions require understanding of core concepts and practice. PracHub provides solutions with explanations to help you master system design interviews.

Q: What difficulty level is this interview question?

This is a hard difficulty System Design question, commonly asked during Onsite rounds at Roblox.

Q: What role is this question designed for?

This question is commonly asked for Software Engineer candidates at Roblox during technical interviews.

Question

System Design: Resource Loader and ROS-like Publish/Subscribe

Context

You are designing two foundational systems for a large-scale, real-time interactive platform with both client and server components. The platform must run across heterogeneous devices and networks, support low-latency experiences, and scale to millions of users and thousands of services.

Part A — Resource Loader

Design a Resource Loader that supports multiple resource types (e.g., images, configs, ML models, audio). Provide:

Public APIs and data model
How new resource types are plugged in (extensibility)
Async/concurrent loading and cancellation
Prioritization and dynamic reprioritization
Batching and coalescing
Caching: memory and disk; eviction policies; cache keys; validation
Deduplication of in-flight requests
Retries, timeouts, and hedged requests
Dependency resolution (manifests, topological loading)
Streaming/partial loads (e.g., progressive textures, range requests)
Failure isolation and fault containment (e.g., decoder crashes)
Thread-safety and correctness under concurrency
Observability (metrics, logs, tracing)
Deployment, scaling strategies (client/server, edge), and trade-offs

Part B — ROS-like Publish/Subscribe System

Design a ROS-like pub/sub system for distributed nodes (clients, services, simulators, and ML components). Define:

Topics, message schema/serialization, and versioning
Discovery mechanisms (LAN/WAN, NAT) and routing
QoS and reliability options (best-effort vs reliable), delivery semantics
Ordering guarantees (per-publisher, per-key)
Replay and durability options
Backpressure/flow control and handling slow/disconnected subscribers
Partitioning and scaling across nodes and regions
Latency/real-time considerations and zero-copy paths
Clock synchronization and time semantics
Fault tolerance, high availability, and failover
Security (authentication, authorization, encryption)
Comparison and justification of brokered vs brokerless and federated topologies

Be explicit about key trade-offs and justify your choices with concise reasoning.

Design resource loader and ROS-like pub/sub

Quick Overview

Design resource loader and ROS-like pub/sub

System Design: Resource Loader and ROS-like Publish/Subscribe

Context

Part A — Resource Loader

Part B — ROS-like Publish/Subscribe System

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