Build vs Buy Webhook Infrastructure: An Honest Framework

Build vs buy decisions are usually nuanced. Webhook infrastructure isn't. The economics are clearer than most build-vs-buy calls because the surface is well-understood, the work is well-scoped, and the operational cost is large enough to be visible. Here's an honest framework for which side of the line your product belongs on.

What 'build' actually means

Building webhook infrastructure means owning every component in the reference architecture: ingest API, persistence, queue, worker pool, adapters per destination type, attempt log, DLQ, replay tooling, customer-facing UI, alerting, audit trail.

For one webhook destination type, the v1 takes a senior engineer 4–6 weeks. For a production-grade system that handles edge cases (retry classification, idempotency, signing, observability), figure 3–4 months. For each additional destination type, add 2–4 weeks per adapter.

Once shipped, ongoing maintenance is roughly 25–35% of the build cost per year, every year. The system is stateful, customer-visible, and on the hot path of business operations, it can't be ignored.

When 'build' is the right call

There are three legitimate reasons to build:

Reason 1: outbound delivery is your product. If you're a CDP, an iPaaS, or an integration-as-a-service vendor, the delivery layer is the differentiator. You can't outsource it.

Reason 2: you have unique constraints that platforms don't support. If your security model requires data never leaves your VPC, or your latency target is sub-10ms end-to-end, or you have regulatory requirements that need on-prem deployment, platforms may not fit. Verify this is real, not assumed, most "we need it in-house" arguments dissolve under examination.

Reason 3: your scale makes platform pricing unworkable. At very high volumes (billions of events per month), per-delivery pricing on platforms can exceed the cost of running your own infrastructure. Do the math. For most B2B SaaS, this doesn't apply until late-stage.

If none of the three apply, the build case is weak.

When 'buy' is the right call

Buy is the right call when outbound delivery is necessary for your product but not differentiating. This is the case for almost every B2B SaaS:

• You need to send events to your customers' systems.
• Your customers care about reliability, not about whose code is sending the events.
• Engineering time is your scarcest resource and you'd rather spend it on the parts of the product customers actually pay for.

The math is straightforward: a 4-engineer team spending 4 months on webhook v1 costs roughly $300K loaded. Annual maintenance is another $100K-$150K. After two years you've spent half a million dollars on plumbing.

Compare to a platform like Pushrail's Growth plan at $149/month ($1,788/year) for 1M deliveries and 10 destination types. The break-even on building vs buying is somewhere north of 100x your platform bill, which means you'd need to be doing 100M+ deliveries to justify building.

The hidden cost of building

The visible cost is engineering time. The hidden cost is opportunity cost and incident cost.

Opportunity cost. Every engineering month spent on the webhook platform is a month not spent on your actual product. Founders consistently underestimate this, "we'll just build it" sounds cheap until you trace which features didn't ship as a result.

Incident cost. A webhook platform that loses events is a customer-facing incident. Building it yourself means owning the incidents, the post-mortems, and the customer trust repair. Platforms abstract that operational burden, when something goes wrong, they're the ones on call.

Talent cost. Webhook platforms have well-known failure modes (retry storms, duplicate sends, DLQ overflow, signature verification bugs). Building yours means hiring or training engineers who can avoid them. The platform has the institutional knowledge baked into the code.

The argument against buying

Honest counter-arguments to the buy case:

Vendor lock-in. Yes, moving off a platform requires effort. The mitigation: pick a platform with an exit path (data export, well-documented schemas, abstract destination configuration). If you can't pull your delivery configurations out in a structured format, that's a red flag.

Cost growth. Platform bills scale with volume. At very high volumes, the platform can become more expensive than building. Track it: if you're approaching the volume where the math flips, plan the build.

Feature gaps. A platform supports what it supports. If your use case requires a destination type or a feature the platform doesn't have, you have to wait or build the gap yourself. Mitigation: pick a platform with adapter coverage that matches your customer asks.

The decision matrix

Question	Build	Buy
Is outbound delivery your differentiator?	Yes	No
Will you need >5 destination types?	Doesn't matter	Yes (platforms shine here)
Engineering team size?	10+ on platform	Anything smaller
Volume?	>100M/month	<100M/month
Operational tolerance?	High (you're on call)	Low (let the platform handle it)

Almost every B2B SaaS lands in the Buy column on every row. Build is right for a small set of companies; buy is right for most.

How Pushrail fits

Pushrail is a buy-side choice for SaaS teams that need outbound delivery but don't want to build the platform. The destinations catalog covers 18 destination types; the event delivery layer provides the reliability primitives; the embedded portal means your customers configure their own destinations without you building the UI.

If you're evaluating: try the sandbox. The integration is a few hours, and the answer to "should we build this ourselves?" usually becomes clear once you see what's already shipped.

Next and final post in the series: multi-tenant event delivery, the isolation patterns that make tenant-scoped delivery actually safe.