Rebuilding Linear’s delta sync read path

Linear rebuilt its delta sync read path to help local-first clients efficiently catch up on changes after being offline, particularly in large workspaces that can generate nearly one million sync actions daily. Its previous Postgres-based approach became increasingly CPU-intensive and unpredictable because it had to scan large ID ranges while repeatedly filtering actions by user permissions and client subscriptions. The new architecture uses turbopuffer’s inverted indexes, which represent permissions and subscriptions as sorted posting lists of sync action IDs that can be unioned and intersected directly with requested ID ranges. Linear replicates sync-action metadata from Postgres to turbopuffer through a change-data-capture pipeline, then uses a two-stage process that filters lightweight metadata before retrieving full payloads from Postgres only for actions that will be sent to clients. To safely address replication lag, Postgres remains authoritative for a small recent portion of the log, overlapping with turbopuffer results that are deduplicated, while requests can fall back to Postgres when needed. Shadow testing verified that the new path returned the same actions as the existing system, and production results showed more stable p95 and p99 latency as workspaces, permission sets, and sync logs grew.

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