Case study

Time Doctor: moving billing for 280K+ users from Stripe to Paddle

Core parts of an event-driven billing service on NestJS and GCP Pub/Sub, live in about 9 months.

By Saidul Islam Bhuiyan, founder and principal engineer · Updated 10 October 2026

In short

Time Doctor, a workforce analytics SaaS with 280K+ active users, needed to move subscription billing off a legacy service tightly coupled to Stripe. Core parts of the new event-driven billing service were built on NestJS microservices and GCP Pub/Sub, with idempotent Paddle webhooks and an auditable event trail. It went live in about 9 months and contributed to about $18M a year in savings.

Client: Time Doctor, USA
Role: Integrations Engineer
Users: 280K+ active
Time to live: About 9 months
Result: About $18M a year in savings contributed

Workforce analytics SaaS · USA

Time Doctor

timedoctor.com ↗

Integrations Engineer, core billing services

Moving subscription billing for 280K+ users from Stripe to Paddle while the business kept running.

Context

Billing lived inside a legacy service tightly coupled to Stripe. Subscriptions and churn were hard to manage, and partner integrations depended on the same code.

Constraints

Live revenue for 280K+ active users
Partner and third party integrations had to keep working
Every subscription change had to be traceable

Key engineering decisions

Billing split into NestJS microservices that communicate through GCP Pub/Sub events, so subscription, churn and partner flows can change independently
Every Paddle webhook handled idempotently, so a retried delivery never applies twice
An auditable event trail for each subscription and churn change
Legacy partnership services and their data moved onto the new platform with minimal disruption
Infrastructure in Terraform, with 24/7 monitoring and alerts in Datadog

Results

280K+active users on the new billing

9 monthsto go live

$18Ma year in savings it contributed to

Simplified architecture. Service names are descriptive.

NestJS

GCP Pub/Sub

MongoDB

Redis

Paddle

Terraform

Datadog

Lessons for your project

What carries over to other systems

Make every webhook idempotent firstProviders retry deliveries. Deduplicating them is what stops a retry from charging or changing a subscription twice.
Publish billing changes as eventsWhen subscription changes go out as events, other services stop depending on one payment provider.
Keep an auditable trailEvery subscription and churn change recorded as an event makes support, finance and audits straightforward.
Monitor money flows from day oneInfrastructure in Terraform and 24/7 alerts in Datadog catch payment problems before customers do.

Questions

Common questions

Anything else is easier to answer on a short call.

Why move from Stripe to Paddle?

At Time Doctor the legacy payment service was tightly coupled to Stripe, and subscriptions and churn were hard to manage. The new service on Paddle made billing event-driven, auditable and no longer tied to one provider.

How do you migrate billing without disrupting customers?

Billing changes are published as events, every webhook is handled idempotently, and legacy partner services and their data move across with minimal disruption, with 24/7 monitoring throughout.

Can you run a similar migration for us?

Yes. It starts with a 1–2 week discovery and architecture sprint, priced at $1,000 to $2,000, that maps your billing flows and the safest path between providers.

Tell us what you need to build or scale.

Engagements start with a 1–2 week discovery sprint, $1,000 to $2,000. Email [email protected]

Book a call LinkedIn ↗