The engineering bottleneck with assembled stacks
Growth leads assign a variant and record the outcome in two different universes: the experiment platform knows who saw what, the product database knows who converted, and joining them is a quarterly data project. Under that friction, teams run experiments whose results arrive after the decision was already made by shipping deadline.
Architecture on the Software Lifecycle Cloud
Assignment is a pure function of the subject key and the experiment’s salt — stable across requests, no coordination needed. The function records the assignment row once and serves the variant; outcome handlers were already writing events, which now simply carry the experiment id the assignment returned. Analysis reads assignments and outcomes from neighbouring tables with the same keys.
Deterministic beats random
Hashing the subject key means the same user gets the same variant on every device and every request without a lookup table of coin flips — and re-running the analysis reproduces the same buckets. When an experiment smells wrong, the assignments can be recomputed from the rule and compared against what was served; that audit is impossible when a vendor’s black box did the flipping.
- Assignments and outcomes share keys, so the experiment readout is one honest query
- Variant splits and eligibility are table rows — pausing an experiment is an update, not a ticket
- No client-side experiment SDK phoning a third party from your product’s critical path
Statistics stay your responsibility
This pattern assigns and records; it does not supply a statistician. Sample sizes, guardrail metrics, and when-to-call-it judgement belong to your team or your analysis tools reading the exported tables. What the platform removes is the plumbing excuse for not knowing who saw what.
Frequently asked questions
Deterministically: the variant is a hash of the subject key and the experiment salt. Same subject, same variant, every request and device — and assignments are also stored, so served variants can be audited against the rule.
Over the project’s tables: assignments joined to outcome events by subject key. Bring your notebooks or BI to those exports; the platform’s contribution is that the join exists at all, in one place, from day one.
Yes — updating the experiment row ends new assignments, and the full assignment and outcome record remains for the post-mortem. Early stopping is a data change with an author and a timestamp, not a vendor ticket.
Related capabilities, architectures, and comparisons
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