--- title: How Reddit Migrated Comments Functionality from Python to Go description: Reddit migrated their comments functionality from a legacy Python monolith to a Go microservice, handling their largest dataset and highest write throughput.... canonical: https://daily.dev/posts/how-reddit-migrated-comments-functionality-from-python-to-go-arpssir4b twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: How Reddit Migrated Comments Functionality from Python to Go | daily.dev og:description: Reddit migrated their comments functionality from a legacy Python monolith to a Go microservice, handling their largest dataset and highest write throughput.... og:url: https://daily.dev/posts/how-reddit-migrated-comments-functionality-from-python-to-go-arpssir4b og:image: https://api.daily.dev/og/posts/ArpSsIr4B.png og:image:alt: How Reddit Migrated Comments Functionality from Python to Go og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # How Reddit Migrated Comments Functionality from Python to Go **[ByteByteGo](https://daily.dev/sources/bytebytego)** · 11 min read · 237 upvotes · 2 comments ## Summary Reddit migrated their comments functionality from a legacy Python monolith to a Go microservice, handling their largest dataset and highest write throughput. The migration used "tap compare" for read operations and "sister datastores" for writes, allowing validation with real traffic while maintaining zero risk. Key challenges included cross-language serialization issues, database access pattern differences, and race conditions in verification. The migration succeeded with zero user disruption and delivered an unexpected bonus: p99 latency was cut in half, dropping from occasional 15-second spikes to consistently under 100 milliseconds. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Community discussion Top comments from developers on daily.dev. **@xidib78169** · 0 upvotes > I've also recently started writing my own applications in go, but since I don't want to deal with database operations, I've been using go only partially. > In that sense, the approach described in this post receiving the entire request in go and filling in the differences was quite interesting. > I still feel some resistance to writing everything in go, but this struck me as one useful technique for switching from language A to language B. ## Similar posts on daily.dev - [Reddit Migrates Comment Backend from Python to Go Microservice to Halve Latency](https://daily.dev/posts/reddit-migrates-comment-backend-from-python-to-go-microservice-to-halve-latency-femv8iz3b) · InfoQ · 1 upvotes · 0 comments - [Inside Look at Reddit's Metadata Store](https://daily.dev/posts/inside-look-at-reddit-s-metadata-store-g4g3f9yai) · System Design Codex · 14 upvotes · 0 comments --- Tags: [#python](https://daily.dev/tags/python), [#golang](https://daily.dev/tags/golang), [#microservices](https://daily.dev/tags/microservices) [View this post on daily.dev](https://daily.dev/posts/how-reddit-migrated-comments-functionality-from-python-to-go-arpssir4b) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"How Reddit Migrated Comments Functionality from Python to Go","url":"https://daily.dev/posts/how-reddit-migrated-comments-functionality-from-python-to-go-arpssir4b","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/how-reddit-migrated-comments-functionality-from-python-to-go-arpssir4b"},"datePublished":"2025-12-07T16:35:38.249Z","dateModified":"2025-12-07T16:36:03.362Z","description":"Reddit migrated their comments functionality from a legacy Python monolith to a Go microservice, handling their largest dataset and highest write throughput....","image":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/b89f26a3800e8657fa49db1b3c32f289?_a=AQAEulh","thumbnailUrl":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/b89f26a3800e8657fa49db1b3c32f289?_a=AQAEulh","isAccessibleForFree":true,"articleSection":"ByteByteGo","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"ByteByteGo","logo":"https://media.daily.dev/image/upload/t_logo,f_auto/v1/logos/35be29234ee14d01a9cd049c52e12753","url":"https://daily.dev/sources/bytebytego"},"commentCount":2,"discussionUrl":"https://daily.dev/posts/how-reddit-migrated-comments-functionality-from-python-to-go-arpssir4b","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":237},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":2}],"keywords":"python,golang,microservices","timeRequired":"PT11M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"ByteByteGo","item":"https://daily.dev/sources/bytebytego"},{"@type":"ListItem","position":3,"name":"How Reddit Migrated Comments Functionality from Python to Go"}]} {"@context":"https://schema.org","@type":"WebPage","@id":"https://daily.dev/posts/how-reddit-migrated-comments-functionality-from-python-to-go-arpssir4b","comment":[{"@type":"Comment","text":"I’ve also recently started writing my own applications in go, but since I don’t want to deal with database operations, I’ve been using go only partially.\nIn that sense, the approach described in this post receiving the entire request in go and filling in the differences was quite interesting.\nI still feel some resistance to writing everything in go, but this struck me as one useful technique for switching from language A to language B.","datePublished":"2026-01-29T04:12:00.079Z","url":"https://daily.dev/posts/ArpSsIr4B#c-hAv3U07sE","author":{"@type":"Person","name":"test","url":"https://daily.dev/xidib78169","image":"https://media.daily.dev/image/upload/s--O0TOmw4y--/f_auto/v1715772965/public/noProfile"}}]} ```