What is App Stack Builder?

App Stack Builder is a free AI-powered tool that helps founders and developers choose the right tech stack for their projects based on budget, app type, team size, and skill level.

What is the best tech stack for SaaS in 2026?

The best tech stack for SaaS in 2026 typically includes Next.js 16 for frontend, Supabase for database and auth, Vercel for hosting, Stripe for payments, and PostHog for analytics. App Stack Builder can generate a personalized recommendation based on your specific budget and requirements.

Is App Stack Builder free to use?

Yes, App Stack Builder is completely free to use. You can generate unlimited tech stack recommendations without any cost.

What types of apps can I build with the recommended stacks?

App Stack Builder supports various app types including SaaS applications, web apps, mobile apps, e-commerce stores, internal tools, and AI/ML products.

How much does a SaaS tech stack cost per month?

A modern SaaS tech stack can cost anywhere from $0-50/month for bootstrapped startups using free tiers, $100-300/month for growth-stage startups, to $500+/month for enterprise-ready infrastructure. App Stack Builder helps you find the best tools within your specific budget.

What is the best tech stack for solo founders?

For solo founders, we recommend Next.js + Vercel (free), Supabase (free tier), Supabase Auth (free), Stripe (pay as you go), and Plausible or PostHog for analytics. This stack can run your entire SaaS for under $50/month.

Can I export my tech stack recommendations?

Yes, you can export your tech stack recommendations as a PDF document or copy them to your clipboard. You can also share a link to your stack with others.

LLM Observability & EvalsFree tier

Langfuse: Pricing, Features & Alternatives

Langfuse is the most widely deployed open-source platform in this category: traces, cost and latency per call, datasets, LLM-as-judge evals and a versioned prompt registry. ClickHouse acquired it in January 2026, and the MIT licence and self-hosting path were kept. The cloud prices by units (traces, observations and scores) rather than seats. Core is $29/month for 100k units and 90 days of data, and each extra 100k units is $8. Pro at $199 buys three years of retention rather than more volume.

Langfuse Pricing Plans (2026)

Plan	Price	Highlights
Hobby	$0	50k units / month · 2 users · 30 days of data access
CorePopular	$29 / month	100k units / month included · $8 per extra 100k units · Unlimited users
Pro	$199 / month	100k units / month included · $8 per extra 100k units · 3 years of data access
Self-hosted	$0 (self-hosted, MIT)	Docker Compose and Kubernetes templates · Same core product as the cloud

Pricing summary: Free · paid from $29/mo. Always confirm current pricing on the official site.

Key Langfuse Features

100k units / month included
$8 per extra 100k units
Unlimited users
90 days of data access

Pros

+Genuinely open source and self-hostable
+Unit pricing does not punish adding teammates
+Framework-agnostic: OpenTelemetry, LangChain, LlamaIndex, raw SDKs
+Prompt management and evals in the same tool as tracing

Cons

−Self-hosting at scale means running ClickHouse, Postgres and Redis
−Units add up quickly for agent traces with many spans
−Longer retention is gated behind the $199 plan

Best Langfuse Alternatives

Compare all

Braintrust

Free · paid from $249/mo

LangSmith

Free · paid from $39/seat/mo

OpenTelemetry

Free

Langfuse Compared

Langfuse vs Braintrust Langfuse vs OpenTelemetry Langfuse vs LangSmith

Langfuse FAQ

What is Langfuse used for?⌄

Langfuse is a llm observability & evals tool. Open-source LLM tracing, evals and prompt management: MIT-licensed, self-hostable, and $29/month in the cloud with unlimited users.

Is Langfuse free?⌄

Yes — Langfuse has a free tier you can start with, and paid plans for more usage and features.

How much does Langfuse cost?⌄

Langfuse offers a free tier, with paid plans starting at $29/month.

What are the best Langfuse alternatives?⌄

Popular Langfuse alternatives include Braintrust, LangSmith, OpenTelemetry. Compare pricing and features on our Langfuse alternatives page.