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RxDB VS Underlayer

Compare RxDB VS Underlayer and see what are their differences

RxDB

A fast, offline-first, reactive Database for JavaScript Applications

Rating
0 reviews
Pricing
Open source Freemium €400 / Annually
Alternatives Is it good?
Underlayer

Build courses by API, drop them into your product with one iframe, and get told who finished. No portal, no learner accounts, priced per course view.

Rating
0 reviews
Pricing
Freemium $149 / Monthly
Alternatives Is it good?
boldrouter
A unified, OpenAI-compatible gateway to every major LLM provider. One endpoint, one key, one bill - with automatic routing and failover. sponsored
Note: These products don't have any matching categories. If you think this is a mistake, please edit the details of one of the products and suggest appropriate categories.

Which is more popular?

Based on our record, RxDB seems to be more popular. It has been mentioned 14 times since March 2021.

social mentions
14 vs 0
NoSQL Databases popularity
100% vs 0%
alternatives listed
119 vs 2

Base details

Website, pricing, platforms and company facts side by side.

RxDB
Underlayer
Website rxdb.info underlayerhq.com
Pricing
Open source Freemium €400 / Annually Official pricing
Freemium $149 / Monthly Official pricing
Company 2016 Startup from the United Arab Emirates · 1 - 9 employees · 2026
Listed in
NoSQL Databases Databases Developer Tools JavaScript Document Databases +2
Education E-learning Education / E-Learning

About RxDB and Underlayer

In their own words, as submitted to SaaSHub.

RxDB
Underlayer

RxDB, which stands for Reactive Database, is a JavaScript-based NoSQL database designed for a wide range of applications such as websites, hybrid apps, Electron apps, progressive web apps, and Node.js. The "reactive" aspect of RxDB allows you not only to retrieve the current state of the database...

Read more about RxDB

Underlayer is headless, API-first training for SaaS products. Instead of sending your users to a separate LMS portal, you generate a course, embed it where they already work, and get every completion sent back to your own systems. How it works Create a course. Generate one from a doc or a prompt...

Read more about Underlayer

Features and specs

What each product offers, as listed by its team.

RxDB 5 features
Underlayer 0 features
  • Offline-First Architecture
    RxDB is designed with an offline-first approach, allowing applications to function seamlessly without a constant internet connection by utilizing local storage and synchronizing with the server when online.
  • Reactive Data Stores
    The library offers real-time data synchronization and reactive data stores, enabling automatic updates to the UI when the underlying database changes.
  • Cross-Platform Compatibility
    RxDB works across various platforms, including web browsers, Node.js, and mobile devices, providing flexibility for developers in building cross-platform applications.
  • Flexible Schema Management
    RxDB supports JSON Schema for defining data models, allowing developers to enforce data consistency and validation effectively.
  • Replication and Sync
    Comes with built-in replication features that ensure easy data synchronization between client and server databases, helping maintain data consistency across different devices and users.

No features have been listed yet.

Videos

Walkthroughs and reviews on video.

RxDB 0 videos + Add
Underlayer 1 video + Add

No RxDB videos yet. You could help us improve this page by suggesting one.

Underlayer demo

Category popularity

How often each product is chosen within a category, 0–100% relative to the other.

Score bands 0–20 21–40 41–50 51–60 61–100
RxDB
Underlayer
100% 100%
NoSQL Databases
0% 0%
0% 0%
Education
100% 100%
100% 100%
Databases
0% 0%
0% 0%
E-learning
100% 100%

Questions & Answers

As answered by people managing RxDB and Underlayer.

Who are some of the biggest customers of your product?

Underlayer's answer:

it's pre-launching

What makes your product unique?

Underlayer's answer:

Underlayer is training with no portal. You build a course by API, by MCP, or in the visual builder, and add it to your product with one iframe. Then signed webhooks tell your systems who finished. Learners never create an account or leave your app, and the player uses your theme, so it looks like part of your product. We charge per course view, not per seat, and every price and overage rate is published.

Why should a person choose your product over its competitors?

Underlayer's answer:

Most course tools, like Coassemble, Trainn and LearningStudioAI, assume training happens on their own site: learners sign up, log in and get enrolled, and you pay per seat. Underlayer takes the opposite approach:

No learner accounts. You pass in your own user IDs and we track progress against them. Built for developers. A full REST API covers every resource, and an MCP server lets AI agents create and edit courses. Results in your own tools. Signed webhooks send completions to your CRM, your product or your data warehouse. SCORM 1.2 and 2004 export for customers who still need to load courses into an LMS. Public pricing. Plans start at $149/month for 25,000 course views, with unlimited learners and no sales call required.

How would you describe the primary audience of your product?

Underlayer's answer:

SaaS product, customer success and engineering teams who want onboarding, product education or compliance training inside their own app. It also suits platforms that train other people's users, like partner networks, marketplaces and field-ops tools, where a separate LMS login gets in the way.

What's the story behind your product?

Underlayer's answer:

Every company putting training in front of its users hit the same wall: the LMS wanted to own the learner. That meant a separate portal, a second login and a per-seat bill for people who never opened a course. We built Underlayer as the layer underneath instead. You keep the product and the user relationship. We handle building the course, playing it and tracking progress, and we stay out of the way.

Which are the primary technologies used for building your product?

Underlayer's answer:

Next.js 16 (App Router) with React 19 and TypeScript, Tailwind CSS v4, and Supabase (Postgres with row-level security, Auth and Storage). Claude from Anthropic generates courses with AI. Stripe handles billing and Resend sends email. There is also a remote MCP server with OAuth 2.1 for AI-agent access.

User comments

Share your experience with using RxDB and Underlayer. For example, how are they different and which one is better?

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Reviews and articles

External articles and on-site reviews we used to compare the two products.

RxDB no reviews yet
Underlayer no reviews yet

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Social recommendations and mentions

Recommendations tracked on public social media and blogs since March 2021.

RxDB 14 mentions
Underlayer 0 mentions
  • Offline-First Landscape – 2025
    I’m doing offline-first apps at work and want to emphasize that you’re constraining yourself a lot trying to do this. As mentioned, everything fast(ish) is using SQLite under the hood. If you don’t already know, SQLite has a... - Source: Hacker News / about 1 year ago
  • Stop Syncing Everything
    > I'm thinking to give it a try in one of my React Native apps that face very uncertain connectivity. Some similar stuff you may want to investigate (no real opinion, just sharing since I've investigated this space a bit): -... - Source: Hacker News / over 1 year ago
  • Show HN: Triplit – Open-source syncing database that runs on server and client
    Looks like it could be a more batteries-included/opinionated alternative to RxDB (https://rxdb.info). The relational queries might help some people who tend to think in SQL as opposed to documents (as in CouchDB or MongoDB) and the... - Source: Hacker News / over 2 years ago

View more

Tracking Underlayer since Sep 2026.

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