How we scaled Slack to support 1000s of developers
In this technical retrospective (2025), @eckles shares practical architectural lessons learned from running, scaling, or migrating production software under lean constraints.
Core Principles for Independent Builders:
Defaulting to simpler architectures (such as monolithic frameworks, SQLite, or managed VPS) prevents early engineering bankruptcy.
Evaluating true compute and egress costs reveals that high cloud bills can often be slashed by 80%+ through judicious re-platforming.
Code you write at 2 AM as a solo engineer must be easy to debug six months later without complex microservice dependencies.
Community Debate Themes:
HN engineers debated the tradeoffs between cloud convenience and raw server economics, database indexing strategies, and resisting premature architectural complexity.
CATEGORY Frugal Engineering →
HISTORICAL ERA Post-ZIRP & AI (2023–2026)
COMMUNITY SCORE ★ 173 points
TOTAL DISCUSSIONS 118 comments
Does it mean that it forces the customers to send 50 messages instead of a single mail message?
Always feels awkward when there are general statements about the group you belong to, which are certainly false at least for you, and possibly for most others you know in that group.
If anything, I would expect developers to dislike a web chat, as tech-savvy people generally seem to prefer more lightweight and customizable options.
Much of the post reads like a rather annoying advertisement.
I was curious why it was a problem to support thousands of customers in the first place, and looks like the issues were in combining conversations over different communication channels, and that a single overloaded person used to create those Slack chats.
It's a cool idea that the end users can chat easily with the teams who build the product. (If I got that right, I think that's part of what is offered here.) Where I work, we have several layers in between engineering and the end users and ... while there's a lot to be said for increasing focus and reducing distractions, I think it's also nice to have the unfiltered contact sometimes.
I prefer email. Email is asynchronous, It does not interrupt my flow or my presentations,
I can decide when I spend tine responding. Then I can fully focus on the emails and type the response they merit.
Of course you have the person sending you an email and 30s later they tap you on the shoulder to ask if you got that email.
I don't mind email, but I despise Slack.
I miss the olden days of being able to check my email once or twice a day with nobody expecting an immediate response, and being able to focus the rest of the time.
Three or four times a year, in response to something genuinely urgent, I might get a phone call.
Regarding various comments here preferring email... let me say that I far, far prefer chat (and the instant notifications!). I would prefer Discord, but I'm just glad it's chat.
After saying that, let me share that Railway is incredible and very affordable.