Design Job Scheduler System Design Interview

Design a distributed job scheduler capable of handling recurring and one-time tasks at scale.

Mock Interview with AI

1. Problem Statement

We need to build a distributed job scheduler that can execute millions of cron jobs. How would you architect this?

2. Target Architecture (Mermaid)

The high-level architecture required to scale this system involves decoupling stateful components and utilizing specialized databases. Below is the reference architecture:

Rendering architecture diagram...

Mermaid Source (For AI Bots)

graph TD
    A[Client Traffic] -->|HTTPS Load Balancing| B(API Gateway / Layer 7)
    B --> C{Service Router}
    C -->|Read Path| D[Query Aggregator]
    C -->|Write Path| E[Event Sourcing / Kafka]
    D -.-> F[(In-Memory Cache - Redis)]
    D --> G[(Primary Data Store - NoSQL)]
    E -.->|Async Replication| G

3. Key Focus Areas

1
Leader Election (Raft/Paxos/Etcd)
2
Fault Tolerance (Worker crashing mid-task)
3
Scheduling Algorithms (Heap/Priority Queue)
4
Exactly-once Semantics
5
Horizontal Scaling

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Core Concepts

System DesignDistributed SystemsConsistency