---
title: "Latest reads"
description: "The engineering internet, summarised so you can actually read it."
---

# Latest reads
> The engineering internet, summarised so you can actually read it.

## Articles

### [How to Use Quasi-experiments and Counterfactuals to Build Great Products](https://yomu.fyi/post/how-to-use-quasi-experiments-and-counterfactuals-to-build-great-produc.md)
- Company: [Shopify](https://yomu.fyi/company/shopify.md)
- Author: 2023-10-18
- Published: Sep 28, 2020
- Type: Explainer

Correlation does not establish causation, so the post presents causal inference as a way to determine why product metrics change and to validate or invalidate business strategies. The proposed evidence ladder places randomized A/B tests first, quasi-experiments such as fixed-effects regression and difference-in-differences second, and counterfactual estimation third, with descriptive statistics providing no direct causal evidence. It explains that quasi-experiments use non-random treatment and control divisions, while difference-in-differences depends on a parallel-trends assumption and fixed-effects regression assumes relevant dividing factors were collected. For a security update released to everyone, the team trained a time-series model on unaffected feature usage and global activity trends, then found no lift versus actual usage, indicating no negative effect on usage. Because observational methods bring greater uncertainty and frequent false positives, the post recommends stating assumptions, relaxing them through robustness checks, and using DAGs and Dagitty to test causal hypotheses.


### [Migrating Heroku Database Apps To Fly](https://yomu.fyi/post/migrating-heroku-database-apps-to-fly.md)
- Company: [Fly.io](https://yomu.fyi/company/fly-io.md)
- Published: Sep 25, 2020
- Type: Tutorial

Migrating a Heroku application to Fly requires attention to database connectivity because Heroku Postgres must be accessed over SSL from outside Heroku. The post uses the DATABASE\_URL environment variable, parses it with pg-connection-string, and passes a configured connector to Massive.js, setting sslmode to require and rejectUnauthorized to false to accommodate self-signed certificates in Heroku Postgres’s certificate chain. It also shows a local-development fallback that uses a non-SSL localhost Postgres connection when DATABASE\_URL is undefined. With these changes, Turboku can migrate the app and convert DATABASE\_URL into a Fly secret, while the application retains its database connection and can use Fly’s region and scaling controls. Database latency still depends on proximity to Heroku’s US or European database regions, so caching within Fly regions may matter for mission-critical performance.


### [Our Journey to Continuous Delivery at Grab (Part 1)](https://yomu.fyi/post/our-journey-to-continuous-delivery-at-grab-part-1.md)
- Company: [Grab](https://yomu.fyi/company/grab.md)
- Author: Sylvain Bougerel
- Published: Sep 23, 2020
- Type: Problem & solution

Around the end of 2018, Grab's backend architecture consisted of roughly 270 services managed through fragmented, manual deployment workflows. Engineers copied release parameters between build logs, wiki pages, Slack bots, and multiple Jenkins jobs, leading to high operational friction and an average of 10 business days between production updates for a service. To streamline delivery, Grab built Conveyor, an internal automation platform built on top of open-source Spinnaker. Conveyor introduced a custom user interface focused on pipeline visibility and a pipeline-as-code DSL called Artificer using Jsonnet files in the monorepository. The platform automatically registers build artifacts with commit metadata to eliminate manual parameter entry and automatically provisions integration, staging, and production pipelines.


### [Enforcing Modularity in Rails Apps with Packwerk](https://yomu.fyi/post/enforcing-modularity-in-rails-apps-with-packwerk.md)
- Company: [Shopify](https://yomu.fyi/company/shopify.md)
- Author: 2023-10-18
- Published: Sep 23, 2020
- Type: Problem & solution

Large Rails monoliths can develop high coupling, low cohesion, cross-component calls, shared Active Record models, and classes that know too much because Ruby and Rails provide limited boundary enforcement. Shopify created Packwerk, an open-source static analysis tool that groups Ruby files into packages and enforces dependency and privacy boundaries, including controlled public APIs for constants. It reports the violation type and location with actionable next steps, integrates with CI, and can run locally; installation begins by adding the gem and running packwerk init. Because Ruby static analysis is complex, Packwerk ignores constants that are not autoloaded, reducing false positives at the cost of false negatives. The excerpt says it runs in six Shopify Rails applications, with 48 packages and 30 boundary enforcements in the core codebase, while adoption also prompted work on dependency inversion.


### [The Life-Changing Magic of Tidying Ruby Object Allocations](https://yomu.fyi/post/the-life-changing-magic-of-tidying-ruby-object-allocations.md)
- Company: [Heroku](https://yomu.fyi/company/heroku.md)
- Author: Richard Schneeman
- Published: Sep 16, 2020
- Type: Explainer

The post presents object-allocation profiling as a way to find Ruby performance hotspots, including code inside libraries such as Active Record. It uses memory\_profiler and derailed\_benchmarks to group allocations by gem, file, and source location, then examines whether each allocation can be removed or avoided. A benchmark compares a direct maximum comparison with an array-based version: the array allocation makes the latter 2.04x slower in the reported run. One optimization for cache\_version reuses a raw database timestamp string when it is safe, checking its type, format, timezone, and provenance before deleting separators and padding PostgreSQL-truncated values. This change reduces allocation from 743,842 bytes and 6,626 objects to 702,955 bytes and 6,063 objects, and the post reports up to 1.12x faster; combined optimizations reach 1.23x overall.


### [Under Deconstruction: The State of Shopify’s Monolith](https://yomu.fyi/post/under-deconstruction-the-state-of-shopify-s-monolith.md)
- Company: [Shopify](https://yomu.fyi/company/shopify.md)
- Author: 2023-10-18
- Published: Sep 16, 2020
- Type: Explainer

Shopify describes the ongoing effort to modularize its core Ruby on Rails monolith, which contains more than 2.8 million lines of Ruby and 500,000 commits. The initiative organizes code into independently owned components intended to narrow developer focus, reduce affected test suites, preserve contracts, and clarify operational ownership, while recognizing that large-scale refactoring is also a people problem. The work has already improved exception triage, distributed codebase chores, and design awareness, while its current practices emphasize grassroots participation, tooling, targeted reviews, and a holistic architectural view. Packwerk restricts dependencies for about a third of the 37 main-monolith components. Shopify is pursuing a cleaner dependency graph, componentized Rails applications by default, and isolated component tests, while reserving service extraction for cases such as storefront rendering and credit-card vaulting.


### [Supabase Hacktoberfest 2020](https://yomu.fyi/post/supabase-hacktoberfest-2020.md)
- Company: [Supabase](https://yomu.fyi/company/supabase.md)
- Author: Thor Schaeff
- Published: Sep 11, 2020
- Type: Announcement

Supabase announced its participation in Hacktoberfest 2020 by organizing a series of community events and open-source contribution activities. Contributors can attend scheduled live broadcasts, including a GitHub Open Source Friday stream featuring @kiwicopple on Twitch alongside an online introductory meetup hosted on YouTube. To coordinate development, Supabase launched a GitHub project board containing tasks and idea notes, requiring participants to label new issues with the hacktoberfest tag for official challenge qualification. Available engineering efforts span creating framework examples for Blitz.js and Redwood.js as well as writing specialized Postgres templates for diverse use cases. Non-code contribution pathways are also supported, encouraging community members to submit documentation improvements, user experience adjustments, illustrations, custom loading pages, or Lottie animations.


### [Always Be Connecting (with HTTPS)](https://yomu.fyi/post/always-be-connecting-with-https.md)
- Company: [Fly.io](https://yomu.fyi/company/fly-io.md)
- Published: Sep 11, 2020
- Type: Tutorial

The post explains how to ensure users reach an HTTPS version of an application running behind Fly’s edge proxies, particularly when a custom domain and certificate are attached. Fly’s default fly.dev behavior redirects HTTP automatically, but custom certificates do not activate that upgrade because connection behavior remains under the application owner’s control. The recommended method checks the X-Forwarded-Proto header, which records whether the original client connection used http or https, and returns a 301 redirect to the same URL with an https scheme when needed. Examples implement the check in Go middleware, Express middleware for Node, and Nginx configuration; the post also notes that non-Fly deployments can inspect the request and URL scheme instead, while Fly was considering future automation.


### [Block Sparse Matrices for Smaller and Faster Language Models](https://yomu.fyi/post/block-sparse-matrices-for-smaller-and-faster-language-models.md)
- Company: [Hugging Face](https://yomu.fyi/company/hugging-face.md)
- Author: François Lagunas
- Published: Sep 10, 2020
- Type: Announcement

Full dense layers in neural networks are often unnecessarily large and can be pruned without sacrificing precision, but available sparse algebra tools and PyTorch native implementations lack efficiency. To resolve this issue, the pytorch\_block\_sparse extension introduces BlockSparseLinear as a drop-in replacement for standard linear layers alongside BlockSparseModelPatcher for on-the-fly model modifications. The library uses NVIDIA CUTLASS C++ CUDA templates derived from Yulhwa Kim's cutlass tilesparse proof of concept. Although baseline sparse operations remain roughly twice as slow as cuBLAS-optimized dense counterparts, performance scales with sparsity, making a 75% sparse matrix approximately two times faster than a dense layer while reducing memory consumption by four times. Future updates will target dynamic sparsity optimization and NVIDIA Ampere Tensor Core primitives.


### [Tophatting in React Native](https://yomu.fyi/post/tophatting-in-react-native.md)
- Company: [Shopify](https://yomu.fyi/company/shopify.md)
- Author: 2023-10-18
- Published: Sep 9, 2020
- Type: Tutorial

Shopify’s tophatting process manually verifies coworkers’ changes before pull requests are approved, but React Native reviews previously required saving work, switching branches, rebuilding, and loading the app. The new tool stores compressed JavaScript bundles and their assets in cloud storage when Shopify Build’s CI pipeline processes a React Native pull request. A backend service records metadata such as the app ID, commit SHA, and branch, generates signed URLs, and posts a pull-request comment with a QR code, bundle ID, and download link. A React Native component library handles deep links through a separate Tophat screen, confirms bundle metadata, downloads and decompresses the selected bundle, saves metadata locally, and restarts the app with it. The first iteration lets developers load peer changes within seconds, and almost all Shopify React Native projects now use the tool.


### [Uncovering the Truth Behind Lua and Redis Data Consistency](https://yomu.fyi/post/uncovering-the-truth-behind-lua-and-redis-data-consistency.md)
- Company: [Grab](https://yomu.fyi/company/grab.md)
- Author: Allen Wang
- Published: Sep 7, 2020
- Type: Incident / postmortem

Grab experienced replica CPU usage spikes following service deployments in their master/replica Redis cluster, which caused failovers to spike to 100% CPU. Investigation revealed that a post-deployment Lua monitor script executed separately on both nodes and relied on non-deterministic HGETALL key ordering. Redis encodes hash objects as either ziplists or hashtables, and restoring from an RDB snapshot initializes small hashes as ziplists even if the master previously converted them to hashtables. This encoding discrepancy caused key ordering to diverge, preventing secondary data from deleting correctly and bloating dataset sizes. Grab resolved the issue by sorting the outputs of HKEYS and HGETALL within the Lua script to guarantee deterministic execution across nodes.


### [Supabase Alpha August 2020](https://yomu.fyi/post/supabase-alpha-august-2020.md)
- Company: [Supabase](https://yomu.fyi/company/supabase.md)
- Author: Paul Copplestone
- Published: Sep 3, 2020
- Type: Announcement

Six months into developing its hosted database platform, Supabase announced updates focusing on authentication, table view management, and community developer tooling. Users can now create database tables and columns directly from the table view interface as well as invite team members to their organizations. The authentication system introduced configurable email confirmations for new user registrations, allowing administrators to toggle confirmations and edit email templates directly from the dashboard. Community contributors added TypeScript support to Supabase, implemented UMD support in supabase-js, and began building Python client libraries starting with postgrest-py. Supabase is preparing to transition from Alpha to Beta by stabilizing its Auth API, improving dashboard performance, and benchmarking platform systems.


### [More Fly Answers To Questions](https://yomu.fyi/post/more-fly-answers-to-questions.md)
- Company: [Fly.io](https://yomu.fyi/company/fly-io.md)
- Published: Sep 2, 2020
- Type: Explainer

This Q&A addresses three operational questions about Fly: running non-HTTP applications, identifying connection IP ranges, and renaming applications. Non-HTTP apps need a network service for Fly’s default TCP or optional HTTP health checks; otherwise, Fly may kill them, although Worker process support is planned. For connectivity controls, Fly says AS40509 ranges may not match source addresses seen by servers and advises treating Fly IPs as changeable, while client certificates over TLS offer improved authentication. Future IPv6 per-application addresses could support firewall allowlists. Renaming currently requires creating a new app with flyctl init, claiming the desired name, changing fly.toml, redeploying, and manually restoring secrets, certificates, hostnames, scaling, regions, and other configuration, while sacrificing the original app’s history.


### [5 Ways to Improve Your React Native Styling Workflow](https://yomu.fyi/post/5-ways-to-improve-your-react-native-styling-workflow.md)
- Company: [Shopify](https://yomu.fyi/company/shopify.md)
- Author: 2023-10-18
- Published: Sep 2, 2020
- Type: Tutorial

Shop's React Native app began as Arrive's codebase, and its visual overhaul prompted a broader rethink of styling practices. The resulting open-source Restyle library organizes styling around a design system covering spacing, semantic colors, and typography, represented by a theme object that components receive through React's Context API. Reusable Box and Text components map props such as spacing, background color, and text variants to theme values, while responsive properties target predefined screen-size breakpoints and TypeScript restricts props to valid theme options with editor autocomplete. The stated result is a more enjoyable and efficient workflow: Restyle supported the transition from Arrive to Shop, enabled theme switching, helped tailor screens to device sizes, and made dark mode easy to add.


### [How to Track State with Type 2 Dimensional Models](https://yomu.fyi/post/how-to-track-state-with-type-2-dimensional-models.md)
- Company: [Shopify](https://yomu.fyi/company/shopify.md)
- Author: 2023-10-18
- Published: Aug 27, 2020
- Type: Tutorial

Application databases often retain only current values in Type 1 dimensions, limiting analysis of historical settings such as feature adoption, retention, and switching behavior. The post explains Type 2 dimensional models through Shopify’s need to track users’ admin languages over time, contrasting application-model changes, scheduled database snapshots, and event logging. Its selected implementation uses Rails after\_commit callbacks to send created or updated records to Kafka, then transforms that event history into records with valid\_from, valid\_to, and is\_current fields using ETL recipes involving PySpark and dbt. The approach provides the required granularity but can miss changes or events, requires delete handling and data-quality checks, and is presented as an iterative solution; MySQL binlogs are described as a more reliable future source.


### [Flyctl Builtins - The Fly Changelog for August](https://yomu.fyi/post/flyctl-builtins-the-fly-changelog-for-august.md)
- Company: [Fly.io](https://yomu.fyi/company/fly-io.md)
- Published: Aug 26, 2020
- Type: Announcement

Flyctl v0.0.139 adds built-in builders for Node, Ruby, Deno, Go, and static web servers, allowing an app to be initialized and deployed without a Dockerfile. The release also lets flyctl init select a public Docker image, stores that choice in fly.toml, and supports repeatable image builds with configurable ports and health checks. Region visibility improves through backup-region listings and a (b) marker in flyctl status, while guided certificate creation supplies DNS instructions for traffic direction and ownership verification. Additional changes include --import, --local-only, timestamped JSON status output, orgs and dns commands, and clearer deployment and authentication messaging. The changelog notes that orgs and dns remain works in progress, and version 0.0.139 fixes an issue with builtin init.


### [ShipIt! Presents: A Look at Shopify's API Health Report](https://yomu.fyi/post/shipit-presents-a-look-at-shopify-s-api-health-report.md)
- Company: [Shopify](https://yomu.fyi/company/shopify.md)
- Author: 2023-10-18
- Published: Aug 25, 2020
- Type: Explainer

On July 17, 2020, ShipIt! hosted a discussion of Shopify’s API Health Report with Shuting Chang, Robert Saunders, Karen Xie, and Vrishti Dutta. The tool was built to surface breaking changes affecting Shopify Partner apps, and the event presented its role alongside the work of the multidisciplinary team behind it. Related materials cover Shopify’s API versioning, including how Shopify manages versioning and breaking changes, plus GraphQL Admin API references, an explorer, and learning resources. The event information also directs questions about API versioning and upcoming migrations to monitored API forums, the Partner Dashboard Support Form, and ShopifyDevs on Twitter, while linking to Shopify Partners, Shopify Developers, and REST/HTTP API evolution material.


### [Securing and Managing Multi-cloud Presto Clusters with Grab’s DataGateway](https://yomu.fyi/post/securing-and-managing-multi-cloud-presto-clusters-with-grab-s-datagate.md)
- Company: [Grab](https://yomu.fyi/company/grab.md)
- Author: Vinnson Lee
- Published: Aug 24, 2020
- Type: Problem & solution

Grab's data engineering team needed to manage data access across growing Presto workloads spanning hundreds of users, thousands of tables, and multiple clouds without exposing infrastructure churn to clients. Out-of-the-box Presto lacked fine-grained schema- and table-level access controls, unified endpoint routing, and seamless cluster switching. To solve this, the team built DataGateway, a smart HTTP proxy and abstraction layer deployed as microservices on Kubernetes. The platform parses incoming SQL statements, verifies user access control lists against target schemas and tables, and dynamically routes queries to appropriate AWS or Azure Presto clusters without requiring endpoint updates. This architecture enabled zero-disruption cluster migrations across 40 clusters and unified access management across a multi-cloud data lake environment.


### [How Shopify Reduced Storefront Response Times with a Rewrite](https://yomu.fyi/post/how-shopify-reduced-storefront-response-times-with-a-rewrite.md)
- Company: [Shopify](https://yomu.fyi/company/shopify.md)
- Author: 2023-10-18
- Published: Aug 20, 2020
- Type: Problem & solution

Shopify rewrote the server-side Storefront Renderer, which loads Liquid themes and storefront data before returning HTML, because the legacy Rails-monolith implementation had developed stricter performance demands and rising time-to-first-byte as traffic grew. The new single-purpose application separates storefront traffic from checkout, admin, and API traffic, uses active-active replication with dedicated read replicas, and adds mechanisms for high-load resilience. During migration, a Ruby verifier compares status codes, headers, and bodies from both implementations, while a custom Lua module on OpenResty samples production traffic and routes requests based on verification results. The rollout had reached more than 90% feature parity, and the new implementation averaged 4x faster server response times, with ongoing work aimed at full parity and retiring the legacy system.


### [Building Reliable Mobile Applications](https://yomu.fyi/post/building-reliable-mobile-applications.md)
- Company: [Shopify](https://yomu.fyi/company/shopify.md)
- Author: 2023-10-18
- Published: Aug 14, 2020
- Type: Explainer

Shopify’s Point Of Sale (POS) app is mission-critical for brick-and-mortar merchants, because downtime can create long lineups, unhappy customers, and lost sales. Unlike server-side systems, mobile fixes depend on Apple and Google review, and merchants may delay installing approved updates, so the team focuses on preventing bugs and shortening recovery time. Its practices include layered automated and manual testing, component ownership with automatic Code Owners reviews, automated mobile “tophatting,” and weekly releases supported by a rotating Release Captain and ShipIt Mobile. Staged rollouts, beta flags, minimum-version enforcement for rare critical security fixes, and dedicated Primary and Secondary ATCs limit exposure and clarify incident response. ChatOps-based incident channels capture findings for root cause analysis, while rotating on-call responsibilities reduce context switching; these measures helped the app scale to larger merchants while shipping faster and improving reliability.


[Newer posts](https://yomu.fyi/posts/page/229.md) · [Older posts](https://yomu.fyi/posts/page/231.md)