How B2B SaaS Companies Build an SDR Function That Feeds Their AEs — Not Competes With Them

An SDR function exists to source and qualify pipeline — not close it. The moment those roles blur, both underperform and you can't tell why. Getting the function right requires four things in sequence: a clear definition of what SDRs own and how it fits alongside your marketing motion, a hiring number derived from your deal math rather than gut, a list built before the first SDR starts, and a pair of hires — never one — so you have diagnostic signal from day one. The variable that determines success: whether the role is defined precisely enough that AEs know exactly what they're receiving and why it's qualified.

Marketing drives leads, SDRs qualify them, AEs close

Before you write a job description, align on what the SDR function is actually supposed to do — and how it sits alongside your marketing motion.

SDRs source and qualify pipeline. AEs close it. The boundary between those roles needs to be documented: what does a qualified handoff look like? What information does the SDR collect before passing to an AE? What does "qualified" mean in your specific vertical — a confirmed budget holder, a prospect using the incumbent software you displace, someone who has experienced the exact operational problem your product solves?

The boundary between SDRs and marketing needs the same clarity. Inbound marketing generates leads. SDRs qualify those leads and convert them into pipeline. SDRs also generate their own outbound pipeline from scratch. These are different workflows with different metrics — you cannot compare inbound lead volume to SDR output and conclude you don't need one because the other is working. You need both. The question is finding the right balance between inbound qualification and outbound prospecting for your specific motion.

In vertical SaaS, where your TAM in a given vertical may be a few thousand companies, the balance often tips toward high-quality outbound sourcing over high-volume inbound qualification. That distinction should shape how you hire, how you measure, and how many SDRs you need.

Work backwards from your deal goal to the number of SDRs you actually need

The right SDR count is a math problem. Do it before you post the job.

Start with your monthly new ARR goal. Determine what share of pipeline will come from SDR-sourced outbound. Divide by your AE close rate to get required pipeline volume. Divide by average ACV to get required opportunities per month. Divide by what one SDR can realistically source per month in your vertical to get SDR count.

Example: if your monthly goal is $10K MRR, SDRs are sourcing 25% of that, your close rate is 30%, and your average deal is $1K MRR — one SDR needs to source roughly 8 qualified opportunities per month. At ten AEs, you need roughly 83 opportunities per month from the SDR function.

The ratio of SDRs to AEs varies significantly by company. How technical is your product? How narrow is your ICP? How large is the reachable prospect universe? These factors matter more than any benchmark ratio. Do the math for your motion specifically.

Build the list before you hire the people

SDRs are only as good as the list they work. Hand them a loose CRM export and tell them to find deals, and you will spend months of runway before concluding — incorrectly — that outbound doesn't work in your vertical. The problem is almost never the outbound motion. It's the list.

Before the first SDR starts, define your ICP with precision: industry vertical, company size, tech stack signals, buying triggers, and geographic focus. Then build the list using databases — ZoomInfo, Sales Nav, Cognism, or industry-specific association directories. For vertical SaaS, the universe is often narrow by design. A field service software company might have 3,000 reachable prospects in their primary ICP. That narrowness is an asset — it means you can build a highly targeted list rather than spraying a broad market.

Aim for 80% accuracy on the initial list. You'll refine it as SDRs make calls and report back. But the SDR should start from a curated set of targets — not build the list themselves while the clock runs.

Hire in pairs, pod with AEs, and build the path to AE

Two SDRs gives you the diagnostic signal one SDR never can. If both underperform, you have a motion problem — fix the list, the messaging, or the process. If one performs and one doesn't, you have a people problem. The distinction determines the response entirely.

Pair each SDR with a specific AE or small set of AEs. The tighter the feedback loop — SDR books a meeting, AE runs it, tells the SDR what the prospect actually cared about — the faster the motion improves. SDRs sourcing into a general pool don't get that feedback. They're making calls without learning from the outcomes.

The best SDRs want to become AEs. Build that path explicitly:

• Set clear promotion criteria (meetings booked, pipeline sourced, conversion rate)
• In some cases, let high-performing SDRs work smaller deals through close — it builds closing experience and creates a natural pipeline for your AE bench
• Always backfill immediately when you promote — pipeline dries up within a quarter if the SDR seat sits open

Promote-from-within SDR programs reduce AE recruiting costs and produce reps who already know your motion, your vertical, and your buyers.

Set metrics that measure quality, not volume

Measuring dials produces volume. Volume produces low-quality pipeline. Low-quality pipeline wastes AE time and generates bad data about whether your outbound motion works.

Measure instead:

• Connection rate — calls that result in a real conversation
• Meeting show rate — booked meetings that actually happen
• Meeting-to-opportunity rate — meetings that convert to qualified AE pipeline

These three metrics tell you whether your list is clean, whether your SDRs are booking real meetings, and whether what they're booking is worth an AE's time.

AEs will always have opinions about lead quality. The only way to evaluate those opinions objectively is through call review and pipeline data — not opinions in response to opinions. Review SDR calls regularly. Look at stage conversion rates by source. The data will tell you whether the AE is right.

Common mistakes founders make with their first SDR team

Most early SDR failures come down to a short list of avoidable errors.

• Measuring activity instead of quality. Fifty dials a day sounds productive. Eight qualified meetings per month that convert to pipeline is the actual number that matters.
• Using SDRs as AE support. SDRs prepping decks, handling follow-up email, or doing prospect research for AEs are not prospecting. These are different jobs. Don't blend them.
• Skipping the tooling. ZoomInfo or a comparable database, an outreach sequencing tool (Outreach.io, Salesloft), and a dialer are table stakes. SDRs without proper tooling are slower and produce worse data from the start.

The pattern: each mistake reflects a failure to define the role clearly before hiring into it. The job description should make scope, tools, metrics, and promotion criteria explicit — before the first SDR starts.

When SDRs aren't the right investment yet

SDR functions work in markets with enough reachable, similar-looking prospects to support outbound volume and an accessible decision-maker profile.

If your ACV is above $100K and deals close through multi-stakeholder relationships, AEs who can open their own pipeline — combined with a conference and referral strategy — will generate better returns than an SDR team cold-calling into enterprise accounts. Build SDRs when the outbound math works: enough reachable prospects at a deal size and close rate where the pipeline volume justifies the team.

Sources

• Bessemer Venture Partners, *Best Practices from Our Portfolio for a High-Performing SDR/BDR Function* — on hiring in pairs, ramp timelines, career path design, and the 80% promote-from-within benchmark
• OnlyCFO, *Math to Evaluate Sales Reps and GTM* — on measuring GTM efficiency and the risk of optimizing for activity metrics
• Mostly Metrics (CJ Gustafson), *5 Ways Finance Can Be More Helpful to Sales* — on finance-to-SDR feedback loops and pipeline quality evaluation

Bessemer Venture Partners, *Best Practices from Our Portfolio for a High-Performing SDR/BDR Function* — on hiring in pairs, ramp timelines, career path design, and the 80% promote-from-within benchmark

OnlyCFO, *Math to Evaluate Sales Reps and GTM* — on measuring GTM efficiency and the risk of optimizing for activity metrics

Mostly Metrics (CJ Gustafson), *5 Ways Finance Can Be More Helpful to Sales* — on finance-to-SDR feedback loops and pipeline quality evaluation