Not chosen because they're popular. Chosen because each one solves a specific problem in the growth funnel, and they're the only combination where all four work together without friction, data loss, or hand-off between teams.
Every tool in this stack has one job. None of them overlap. All four are wired together before anything goes live, so the funnel is tracked, the data is structured, and the emails fire from day one.
Every 100ms of load time costs you conversion rate. Astro's sub-500ms pages and PostHog's lightweight SDK mean you capture data without the site slowing down to collect it.
Supabase is open-source Postgres. PostHog can be self-hosted. You own your user data, your lead data, and your analytics. None of it locked inside a SaaS vendor's proprietary database.
This stack is designed for one person to build and maintain. No separate backend team, no DevOps overhead, no analytics team. It ships fast and it scales when you need it to.
From PostHog event to Loops trigger, every email a lead receives is based on what they actually did, not when they signed up. That's the difference between noise and conversion infrastructure.
Performance Engine
The Problem It Solves
Most frameworks ship megabytes of JavaScript for a page that barely moves. Astro ships zero JS by default. Pages are static HTML served instantly, with React components hydrated only when needed.
Why It Was Chosen
The Islands Architecture means every interactive element hydrates in isolation. The rest of the page is already rendered and done. That's why Astro sites hit sub-500ms load times while Next.js pages are still parsing JavaScript.
Why not Next.js? Next ships a full React runtime on every page. Fast enough for apps. Wasteful for landing pages, marketing sites, and conversion infrastructure where every millisecond is a percentage point of bounce rate.
66%
of Astro sites score good Core Web Vitals
vs 30% for Next.js
90%
less JavaScript than equivalent React apps
zero JS shipped by default
1M
npm downloads per week
and doubling every year
In Production At
Used by Google, Microsoft, Visa, NBC News. Acquired by Cloudflare in January 2026. Now the framework that runs the internet's edge.
Behavioural Analytics
The Problem It Solves
Most B2B SaaS teams are flying blind. GA4 tells you pageviews. Mixpanel tells you funnels. FullStory tells you sessions. LaunchDarkly runs your flags. You're paying for four tools that don't talk to each other.
Why It Was Chosen
PostHog replaces all of them. One SDK captures events that flow simultaneously into analytics, session replay, feature flags, and A/B experiments. When a conversion drops, you click the funnel step and watch the replay. No context switching.
Why not Mixpanel? Mixpanel is analytics only. When you need to understand why a funnel dropped, you're paying for three more tools to find the answer PostHog gives you in one click.
190K+
customers worldwide
98% use it entirely free
65%
of every Y Combinator batch
uses PostHog products
30+
tools replaced by one PostHog install
one SDK. one source of truth.
In Production At
Used by SpaceX, Grafana, and Y Combinator itself. They boosted Startup School engagement 40% using PostHog experiments.
Secure Data Layer
The Problem It Solves
Firebase is fast to start but locks you into NoSQL and proprietary pricing. AWS RDS + Cognito + S3 takes weeks to wire. Most SaaS founders end up in an Airtable-then-migrate nightmare that costs months at the worst time.
Why It Was Chosen
Supabase is real Postgres, not a proprietary database pretending to be. You get a full backend in minutes: database, auth, storage, edge functions, and realtime. Row Level Security lives in the database, not your application code. And you can export and run it anywhere.
Why not Firebase? Firebase is NoSQL. Scaling relational logic on NoSQL is a trap. Supabase gives you the Firebase speed with Postgres power, and you own your data completely.
4M+
developers worldwide
99K+ GitHub stars
$5B
valuation as of October 2025
Series E led by Accel
40%
of the latest YC batch
builds on Supabase
In Production At
Used by Mozilla, GitHub, 1Password, and Perplexity. Lovable and Bolt, two of the top AI coding platforms, run their entire database layer on Supabase. SOC2 Type 2 and HIPAA compliant.
Lifecycle Email
The Problem It Solves
Mailchimp was built for e-commerce newsletters. SendGrid is infrastructure, not a product. SaaS companies end up with marketing emails in one tool, transactional emails in another, and two separate APIs to maintain with zero unified view of what a user has received.
Why It Was Chosen
Loops unifies marketing, product, and transactional email in one platform. Pricing is by contact count, not send volume, so you're not penalized for sending trigger-based emails at scale. One workspace for your whole team, from engineering to revenue.
Why not Mailchimp? Mailchimp charges per contact including unsubscribed ones. It has no unified API for transactional email. And it was built for a newsletter paradigm that has nothing to do with behavioral SaaS lifecycle automation.
100+
Y Combinator startups use Loops
YC W22 backed
$0
per transactional send on all paid plans
vs $0.001–0.003 on SendGrid
1
platform for marketing + product + transactional
not three tools duct-taped together
In Production At
Used by Framer, Spline, and Perplexity. The SaaS-first email platform chosen by the most YC-backed startups.
Built on this stack
No "we'll add tracking later." No "we'll set up email next sprint." The stack is live when the page is live. Retrofitting analytics onto a launched product costs three times as much as starting with it.
From first visit to closed deal. How data flows through all four tools, in order, without any gaps.
Astro serves the page in under 500ms. Static HTML, no waiting for JavaScript to boot. PostHog records the session from the first event.
PostHog tracks scroll depth, click heatmaps, form interactions, and time-on-page. Every event is tied to an anonymous identity that persists across sessions.
Form submission lands in Supabase Postgres. PostHog identifies the user and ties their anonymous session history to their email. No data is lost from before they converted.
Loops fires the welcome email and starts the onboarding sequence. Every subsequent email is triggered by actual user behaviour, not arbitrary day-3 follow-ups.
You see the full picture: what brought them in, where they hesitated, what email converted them. PostHog shows what worked. Repeat.
This flow is live on every project from day one. See it working on your funnel.
I'll audit your setup and tell you exactly what's broken. Usually in the first conversation, within 15 minutes.