Debezium | Techlist.io

pinterestFeb 5, 20263 min readCurated summary

Next Generation DB Ingestion at Pinterest

Pinterest replaced fragmented, batch-oriented database ingestion with a unified Change Data Capture (CDC) framework. The new architecture uses Debezium/TiCDC, Kafka, Flink, Spark, and Iceberg to process only changed records, reducing latency from over 24 hours to minutes while lowering infrastructure costs. It also provides native row-level deletion, scalable operations, and improved compliance. ## Problems with the Legacy System - Batch workflows often delayed updates by more than 24 hours. - Full-table processing was inefficient because many tables changed by less than 5% each day. - Lack of row-level deletion support complicated data compliance. - Multiple independently maintained pipelines created operational complexity and inconsistent data quality. ## Unified CDC-Based Architecture - Supports MySQL, TiDB, and KVStore. - Captures database changes through a generic CDC service and publishes them to Kafka, typically in under one second. - Flink processes events in near real time and stores them in append-only CDC Iceberg tables on S3. - Spark jobs run periodically—often every 15 minutes—to merge recent changes into base Iceberg tables. - A bootstrap pipeline initializes base tables from historical database dumps. - Maintenance jobs handle compaction and snapshot expiration. - The framework is designed for at-least-once processing, petabyte-scale data, thousands of pipelines, and YAML-based configuration. ## CDC Tables and Base Tables - CDC tables act as time-series ledgers containing every change event. - CDC data typically becomes available within five minutes. - Base tables mirror the current state of the source database while retaining historical records. - Base-table latency is generally between 15 minutes and one hour. ## Upserting Changes into Base Tables - Spark first identifies the newest event for each primary key. - Events are ranked by timestamp and GTID, then deduplicated. - Iceberg’s `MERGE INTO` applies the resulting changes: - Deletes matching records when the event represents a deletion. - Updates existing records. - Inserts new records unless the event is a deletion. - The process uses a recent CDC window and a processing watermark to avoid reprocessing unnecessary data. ## Choosing Merge-on-Read - Pinterest standardized on Iceberg’s Merge-on-Read (MOR) strategy. - Copy-on-Write (COW) was rejected for most workloads because: - It requires more computation during writes. - It produces substantially larger replacement files, increasing storage costs. - MOR better balances update performance and storage efficiency for frequent incremental changes. ## Partitioning for Faster Upserts - Large base tables can be partitioned using a hash bucket of the primary key. - For example, `bucket(100, id)` distributes records across 100 partitions. - This allows Spark to process partitions in parallel and reduces the data scanned or rewritten during merges. - Iceberg tables are configured with format version 2, identifier fields, merge-on-read update and delete modes, and target file sizes. ## Small-File Challenge - Bucketing improved parallelism but caused each upsert to generate many small files within partitions. - The article indicates that Pinterest investigated this bottleneck and introduced further optimizations, though the supplied excerpt ends before describing them. Pinterest’s CDC-based design provides a substantially faster and more efficient alternative to full-table batch ingestion. Teams adopting a similar system should combine incremental CDC processing with partitioning, merge-on-read storage, bootstrapping, and ongoing file-maintenance strategies.

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Debezium Apache Kafka Apache Spark Mysql+4

datadogNov 4, 20253 min readCurated summary

Replication redefined: How we built a low-latency, multi-tenant data replication platform

Datadog built a managed, multi-tenant data replication platform to move data reliably across thousands of services without brittle, point-to-point integrations. The effort began by separating analytical search workloads from a shared PostgreSQL database, then evolved into automated pipeline provisioning with Temporal. The platform favors asynchronous replication to improve scalability and resilience, accepting limited replication lag in exchange for lower application latency and reduced operational coupling. ## Scaling Search Beyond PostgreSQL - A shared PostgreSQL database initially provided low-latency access, ACID guarantees, and low operational cost. - As data volumes grew, complex joins and aggregations became increasingly slow. - Datadog’s Metrics Summary page had to join: - 82,000 active metrics - 817,000 metric configurations - Page latency reached approximately 7 seconds at p90, while repeated facet changes generated additional expensive queries. - Index and disk bloat, memory pressure, VACUUM and ANALYZE overhead, and rising I/O wait further reduced throughput. - Rather than continuing to optimize PostgreSQL for analytical search, Datadog moved search and aggregation workloads to a dedicated search platform. - Data was denormalized during replication, producing document-oriented indexes better suited to faceted search. - The resulting system reduced page-load times by as much as 97%—from roughly 30 seconds to 1 second—while maintaining about 500 ms of replication lag. ## Automating Pipeline Provisioning with Temporal Provisioning a replication pipeline required coordinating multiple systems and configuration steps: - Enabling PostgreSQL logical replication with `wal_level`. - Creating users and assigning replication permissions. - Configuring publishers and replication slots. - Deploying Debezium instances to capture PostgreSQL changes. - Creating Kafka topics and mapping them to Debezium instances. - Adding heartbeat tables to monitor replication and prevent excessive WAL retention. - Configuring sink connectors to write Kafka data into the search platform. Manual management became increasingly difficult across many pipelines and data centers. Datadog used Temporal workflows to split provisioning into modular, repeatable tasks and combine them into higher-level orchestrations. This reduced errors, improved consistency, and allowed engineers to create and modify pipelines without repeating complex operational procedures. ## Choosing Asynchronous Replication - Synchronous replication provides strong consistency by waiting for replicas to acknowledge each write. - However, it increases latency and operational complexity, particularly across distributed environments. - Asynchronous replication allows the primary system to acknowledge writes immediately while replicas catch up afterward. - Datadog selected the asynchronous model because it decouples application performance from network latency and replica availability. - The trade-off is temporary replication lag during failures or periods of pressure, but the model offers better scalability and resilience for high-throughput systems. Datadog’s experience suggests that replication should be treated as a managed platform rather than a collection of custom integrations. Separating workloads, automating provisioning, and choosing asynchronous delivery can improve performance and reliability while reducing the operational burden on individual engineering teams.

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Debezium Database Design PostgreSQL Apache Kafka+4