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

What difficulty level is this interview question?

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

What role is this question designed for?

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

Design a scalable key-value configuration service

Quick Overview

This question evaluates expertise in distributed systems and system design, testing competencies in schema and API design, partitioning/sharding, storage engine trade-offs, consistency and replication strategies, and operational features like watches, TTLs, backups, and capacity planning within a multi-region key–value configuration service.

Design a Globally Distributed Key–Value Configuration Service

Background

You are asked to design a globally distributed key–value configuration service powering thousands of microservices across multiple regions. The service should provide low-latency reads, strong safety for updates, and global availability.

Requirements

Define the key schema (namespacing, composability, versioning).
Define the value schema (serialization format, validation, schema evolution).
Explain partitioning/sharding, indexing, and storage engine choices (e.g., LSM-tree vs B-tree).
Describe write/read paths and hot-key mitigation.
Specify the consistency model (linearizable vs eventual), leader election, replication/quorums, and handling of network partitions and failover.
Describe support for transactions, watches/subscribe for updates, TTLs, and backup/restore.
Provide capacity planning, SLAs, multi-region replication strategy, and testing approaches.

Assumptions

Read-heavy (≫95% reads), small values (0.5–8 KB), small key space (≤ few million keys), but very high fanout of clients.
Writes are rare but correctness-critical; clients expect fast propagation of changes.
Multi-tenant namespaces, multi-region footprint, thousands of services, tens of thousands of instances.

Quick Overview

Requirements

Define the key schema (namespacing, composability, versioning).

Define the value schema (serialization format, validation, schema evolution).

Explain partitioning/sharding, indexing, and storage engine choices (e.g., LSM-tree vs B-tree).

Describe write/read paths and hot-key mitigation.

Specify the consistency model (linearizable vs eventual), leader election, replication/quorums, and handling of network partitions and failover.

Describe support for transactions, watches/subscribe for updates, TTLs, and backup/restore.

Provide capacity planning, SLAs, multi-region replication strategy, and testing approaches.

Assumptions

Read-heavy (≫95% reads), small values (0.5–8 KB), small key space (≤ few million keys), but very high fanout of clients.

Writes are rare but correctness-critical; clients expect fast propagation of changes.

Multi-tenant namespaces, multi-region footprint, thousands of services, tens of thousands of instances.

Design a scalable key-value configuration service

Quick Overview

Design a Globally Distributed Key–Value Configuration Service

Background

Requirements

Assumptions

Solution

Submit Your Answer to Earn 20XP

Design a scalable key-value configuration service

Quick Overview

Design a Globally Distributed Key–Value Configuration Service

Background

Requirements

Assumptions

Solution

Submit Your Answer to Earn 20XP