# Migrations
> 24 posts about Migrations, summarised, each linking to the original.

## Articles

### [Migrating Existing Datastores](https://yomu.fyi/post/migrating-existing-datastores.md)
- Company: [Grab](https://yomu.fyi/company/grab.md)
- Author: Nishant Gupta
- Published: Aug 8, 2017

Grab's Identity team faced imminent memory exhaustion on a single Redis node used to cache mobile authentication tokens under rapid user growth. Because read traffic outweighed write traffic by roughly 200 times, the team opted for an AWS ElastiCache cluster with three shards and two read replicas per shard. They executed a zero-downtime, six-phase migration plan while handling a peak load of 20,000 queries per second. The migration transitioned through initial one-time data replication, asynchronous shadow writes, synchronous dual writes, asynchronous read validation, switching primary reads, and final write cleanup. Controlled by feature flags and monitored with metrics at every stage, the migration completed without invalidating tokens or causing service disruptions.


### [Scaling Like a Boss with Presto](https://yomu.fyi/post/scaling-like-a-boss-with-presto.md)
- Company: [Grab](https://yomu.fyi/company/grab.md)
- Author: Aneesh Chandra
- Published: May 1, 2017

Grab experienced severe performance degradation, long queue times, and connection timeouts on its Amazon Redshift analytics cluster as user concurrency and reporting workloads expanded. Although an initial Amazon S3 data lake decoupled storage from compute, business users required standard SQL interfaces rather than Spark data pipelines. The team deployed Presto clusters on AWS EMR, switching their storage format from AVRO to Parquet to support ANSI SQL querying directly against S3. Utilizing a shared Hive metastore on Amazon RDS allowed Grab to adopt a shared-data multi-cluster architecture that isolated distinct workloads across dedicated compute clusters. This setup enabled rapid cluster scaling, streamlined failover, and matched Redshift performance on partitioned time-range queries.


### [Battling with Tech Giants for the World's Best Talent](https://yomu.fyi/post/battling-with-tech-giants-for-the-world-s-best-talent.md)
- Company: [Grab](https://yomu.fyi/company/grab.md)
- Author: Grab Engineering
- Published: Jan 18, 2017

Grab maintains research and development centres across Singapore, Seattle, and Beijing to develop mobility and transaction platforms for Southeast Asia. Engineer Brandon Gao turned down an offer from a major Seattle-based technology corporation to remain at the company due to rapid growth and high engineering impact. During backend infrastructure changes starting in May 2015, Grab transitioned core services from Node.js and Ruby to Golang. A weekend Golang prototype created by Gao evolved into the primary data service linking backend servers to 580,000 drivers across the region. Additionally, his initial work on the User Trust team established a machine-learning risk and fraud detection system supporting large-scale mobile transaction volumes.


### [This Rocket Ain't Stopping - Achieving Zero Downtime for Rails to Golang API Migration](https://yomu.fyi/post/this-rocket-ain-t-stopping-achieving-zero-downtime-for-rails-to-golang.md)
- Company: [Grab](https://yomu.fyi/company/grab.md)
- Author: Lian Yuanlin
- Published: Oct 18, 2016

Grab transitioned its public passenger app APIs from a legacy Rails application to a Golang service-oriented architecture to consolidate its codebase and engineering teams. Initial attempts to proxy traffic through a cloned Rails server via gRPC were abandoned after encountering TCP load imbalances during autoscaling events and memory leaks in the gRPC Ruby gem. The team pivoted to direct logic migration, porting Ruby logic directly into Go while decomposing modules into standalone services. Verification relied on log-based load testing and live shadow testing, where write operations were safely validated using mock data access layers that evaluated expected database outcomes. Production rollout progressed endpoint-by-endpoint using requests-per-second traffic throttling and prewarmed AWS Elastic Load Balancers before executing the final DNS switch.


[Newer posts](https://yomu.fyi/topic/migration.md)