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The dev team behind your HubSpot agency

Slark Labs builds custom HubSpot apps, CMS themes, and complex integrations for HubSpot partner agencies — so your team can focus on strategy and client relationships while we handle the technical builds under your brand.

US-registered LLC · HubSpot-specialist developers · 24-48 hour turnaround · White-label delivery

The HubSpot dev gap most agencies face

Most HubSpot partner agencies are strong on strategy, weak on custom development. Sound familiar?

  • Your team can't build custom HubSpot apps

    You win clients who need marketplace apps, custom CRM integrations, or complex workflows — but your team's expertise is in inbound strategy, not engineering.

  • CMS Hub builds are eating your timeline

    Custom HubSpot themes and modules take 3-4x longer than your team expects. Client deadlines slip, internal resources get stretched thin.

  • Generic dev agencies don't understand HubSpot

    You've tried hiring outside developers. They built things in WordPress logic instead of HubSpot logic. The result was buggy, hard to maintain, and embarrassing to deliver.

  • You're losing HubSpot-heavy projects to bigger agencies

    Without dedicated dev capacity, you can't bid on the more lucrative HubSpot platform projects — even when you're the better strategic fit.

What we build for HubSpot agencies

We're HubSpot-specialist developers. This is what we do every day.

  • Custom HubSpot Apps

    Public marketplace apps and private apps built on the HubSpot Developer Platform with proper OAuth, webhooks, and scalable architecture.

  • CMS Hub Themes & Modules

    Custom themes, modules, and templates built specifically for HubSpot CMS — not WordPress logic applied to HubSpot.

  • HubSpot Integrations

    Connecting HubSpot to anything — Salesforce, NetSuite, Stripe, custom APIs, internal tools. Done right with proper error handling and data sync.

  • Workflow Automations & Custom Code

    Complex workflows with custom code actions, custom data models, and advanced HubSpot operations that go beyond the standard UI.

  • Subscription Billing & Chargebee

    Custom billing flows, Chargebee integrations, and subscription management built into your HubSpot setup.

  • Migration & Data Operations

    Moving from Pardot, Marketo, Mailchimp, or custom CRMs to HubSpot — with clean data transformation and zero downtime.

Trusted by HubSpot agencies

“Slark Labs has been our go-to dev partner for over a year, delivering across multiple client sites including a campaign that helped our client raise nearly $1.2M at a single event. Fast, reliable, no drama — exactly what you need in an agency partner.”

Aaron PlaatTripleskiny

“Slark Labs understood the brief immediately and delivered a precise solution within the quoted timeline. The fix affected hundreds of our clients who are now very happy. Exactly the kind of reliable dev partner an agency needs.”

Lisa Surteesvia Upwork

“Slark Labs are truly full-stack, excelling in both front-end and back-end development. Clear communication throughout, and when faced with difficult challenges they always found a way forward.”

Autumn AlyProject Manager

A recent HubSpot build

4 Custom HubSpot Apps with Shared Backend Architecture case study illustration

4 Custom HubSpot Apps with Shared Backend Architecture

We built 4 custom HubSpot apps for a marketing agency, all running on a single shared backend infrastructure. This let them deploy multiple client apps from one server while keeping client data isolated and secure — significantly reducing infrastructure cost and maintenance complexity.

Tech stack: HubSpot Developer Platform, AWS Lambda, Node.js, OAuth 2.0, Webhooks

4
custom HubSpot apps delivered
1
shared backend serving multiple apps
~70%
reduced hosting cost
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How we work with HubSpot agencies

  1. 1

    Discovery call (30 min)

    We learn about your agency's HubSpot tier, your client mix, and the specific technical work you need support on.

  2. 2

    Scoping document

    For any project we send a detailed scoping document with deliverables, timeline, and fixed price — before any commitment.

  3. 3

    Trial project

    We start with a single small build so you can experience our quality and communication before committing to ongoing work.

  4. 4

    Ongoing partnership

    Once trust is established, we integrate into your tools (Slack, ClickUp, Linear) and become an extension of your team. Sprints, retainers, or project-based — your choice.

Why agencies pick us over generic dev shops

  • HubSpot-native development

    We build in HubSpot logic, not WordPress logic. We understand HubL, custom modules, CMS Hub limitations, marketplace requirements, and OAuth flows.

  • Real production experience

    We've shipped HubSpot apps to production for real agencies serving real clients. Not just tutorials or sandbox builds.

  • US-registered, global team

    Slark Labs is a US LLC based in Wyoming, which simplifies your contracts and accounting. Our developers are vetted and trained on HubSpot specifically.

  • White-label delivery

    Everything we build is delivered under your brand. We can join client calls under your team's banner, write in your tone, and use your tools.

How we compare to your other options

Most agencies have tried hiring generic devs or searching the marketplace. Here's why specialized HubSpot dev is different.

Recommended

Slark Labs

Effective cost
$59–70/hr
HubSpot specialization
HubSpot-native
Marketplace app experience
Yes
CMS Hub expertise
Yes
HubL templating
Yes
Joins client calls
Yes, under your brand
Production reliability
Production-grade
Time to ship
Fast, no ramp

In-house HubSpot Dev

Effective cost
$8,000+/mo + benefits
HubSpot specialization
Yes
Marketplace app experience
Maybe
CMS Hub expertise
Yes
HubL templating
Yes
Joins client calls
Yes
Production reliability
Depends
Time to ship
Limited by capacity

Generic Dev Shop

Effective cost
$150–250/hr
HubSpot specialization
No (WordPress logic)
Marketplace app experience
Rarely
CMS Hub expertise
No
HubL templating
Usually not
Joins client calls
Sometimes
Production reliability
Variable
Time to ship
Slow ramp on HubSpot

Marketplace Freelancer

Effective cost
$50–200/hr
HubSpot specialization
Varies wildly
Marketplace app experience
Mixed
CMS Hub expertise
Mixed
HubL templating
Mixed
Joins client calls
Rare
Production reliability
Inconsistent
Time to ship
Variable
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Engagement models for HubSpot work

Focused HubSpot builds with clear deliverables

Mini Sprint

$5,000

1 week

For: Small features, urgent fixes

  • 1 week of focused development
  • Daily updates
  • Clear deliverable at the end
Book a Discovery Call
Most Popular

Standard Sprint

$9,000

2 weeks

For: Mid-sized builds, focused projects

  • 2 weeks of focused development
  • Daily updates
  • Mid-sprint review and adjustment
  • Clear deliverable at the end
Book a Discovery Call

Extended Sprint

$16,000

4 weeks

For: Larger builds, MVP development

  • 4 weeks of focused development
  • Daily updates
  • Weekly review and adjustment
  • Production-ready deliverable
Book a Discovery Call

Also available: Retainers from $2,800/month for ongoing partnerships · Fixed HubSpot builds from $7,500 for clearly-scoped projects

See all pricing options
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Common HubSpot agency questions

What's your HubSpot experience?

We've built marketplace apps, private apps, custom CMS themes, complex workflow automations, and CRM integrations across multiple HubSpot tiers. Our developers work in HubSpot every day.

Do you understand the difference between marketplace apps and private apps?

Yes. We build both. Marketplace apps require additional security review, OAuth flows, multi-tenant data isolation, and HubSpot's review process. Private apps are simpler but have different limitations. We'll guide you on which is right for each use case.

Can you build for CMS Hub specifically?

Yes. CMS Hub has its own templating language (HubL), module system, and limitations that differ from WordPress or other CMS platforms. We build properly in HubSpot's native system, not workarounds.

How do you handle ongoing maintenance?

HubSpot occasionally pushes platform updates that affect apps and integrations. We monitor for these and update our clients' builds as needed. Retainer clients get this included; project clients can add a maintenance plan.

Can you join our client calls?

Yes, under your brand. We can present technical solutions, explain architecture decisions, and answer technical questions — all positioned as part of your team.

What if my client uses Salesforce + HubSpot?

That's actually one of the more common integrations we build. We handle bidirectional sync, custom field mapping, lead routing, and the data integrity issues that come with multi-CRM setups.

How fast can you start?

For sprint work, usually within 5-10 business days depending on calendar availability. For retainer relationships, we can begin within 5-7 business days after the discovery call.

Do you sign NDAs?

Yes. We work under standard mutual NDAs with all agency clients. This is included in our standard contract.

Let's talk about your HubSpot work

Tell us about your agency, your HubSpot tier, and what you're looking to build. We'll respond within 24 hours.

Prefer to talk first? Book a 30-minute discovery call:

Book a Discovery Call

What happens next

  1. 1We review your message and your agency website
  2. 2We send a response within 24 hours
  3. 3We schedule a 30-minute discovery call at a time that works for you
  4. 4We discuss whether we're a fit — no pressure, no hard sells

Explore Slark Labs