Design Figma's 100x PostgreSQL Multi-Tenant Scaling Architecture

1. Problem Statement & Scope Clarification

System Mission

Design Figma's collaborative cloud database and multi-tenant scaling infrastructure. Figma's multiplayer canvas operates over real-time WebSockets, persisting complex vector document graphs, version trees, user permissions, and comment threads. As Figma scaled $100\times$, its single monolithic AWS Aurora PostgreSQL database experienced severe CPU exhaustion, table lock contention, and replication lag. The platform must scale to hundreds of sharded PostgreSQL nodes with zero downtime, zero data corruption, and seamless cross-shard routing.

Functional Requirements

1. Multi-Tenant Document Persistence: Store hierarchical canvas document trees, node modifications, and organization metadata.
2. Dynamic Shard Query Routing: Route SQL queries transparently to the appropriate database shard based on org_id or file_key.
3. Multiplayer Canvas State Sync: Persist real-time CRDT vector operations without blocking on slow OLTP queries.
4. Live Zero-Downtime Shard Splitting: Split and migrate heavily loaded shards without dropping user WebSocket connections or causing canvas write errors.

Non-Functional Requirements (SLAs & SLOs)

• High Availability: $99.999\%$ uptime for canvas saving and file loading.
• Low Query Latency: $P50 < 1.0\text{ ms}$, $P99 < 8.0\text{ ms}$ on sharded queries.
• Connection Scalability: Support $100,000+$ concurrent application connections via PgBouncer connection multiplexing.

2. Capacity & Scale Estimation (Back-of-the-Envelope Math)

Scale Metrics

• Active Collaborative Design Files: $50,000,000+$.
• Canvas Vector Nodes per File: $10,000 - 1,000,000\text{ nodes}$.
• Peak Query Throughput: $100,000\text{ QPS}$ against the database tier.
• Single PostgreSQL Limits: A maxed-out db.r6g.16xlarge instance (64 vCPUs, 512 GiB RAM) saturates at $\approx 15,000 - 20,000\text{ complex QPS}$.
• Sharding Requirement: $\text{Minimum Required Shards} = \frac{100,000\text{ QPS}}{10,000\text{ safe QPS/node}} \approx \mathbf{10\text{ - } 20\text{ Shard Clusters}}$

3. High-Level Architecture & Component Mapping

Interactive Architecture Diagram
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