Performance tags (N+1, slow, error…)

The profiler runs a single analysis pass once per profile — after every collector, before the profile is persisted — that flags common performance anti-patterns and attaches structured tags to the offending queries and HTTP calls. Tags surface as coloured pills in the panels and on the list page, where a Performance tag filter narrows the profiles down to a given issue.

Detection spans every query collector (typeorm, mikro-orm, mongoose) and the outgoing-HTTP collector (http). Grouping is done once in the core on a per-entry fingerprint each collector supplies (normalized SQL, collection + operation + filter shape, or method + normalized URL), so the same query executed with different bind values is recognised as a repeat.

The detail page leads with a Performance banner summarising the issues, and colour-codes the affected collector tab (and its sub-tabs) by severity so a problematic panel stands out at a glance. Below, a GraphQL query that lists products and resolves each product's reviews from MongoDB (a classic N+1) is flagged N+1 ×4:

Built-in tags

Each tag is a ProfilerTag — { id, label, severity, count?, detail? } — attached to the entry and aggregated (deduplicated) onto profile.tags.

Thresholds

Thresholds live on each collector, so a Mongo slow query and a slow HTTP call can differ. Defaults:

TypeOrmCollectorModule.forRoot({ slowThreshold: 50, nPlusOneThreshold: 2 });
HttpCollectorModule.forRoot({ slowThreshold: 500, largePayloadThreshold: 512 * 1024 });

Migrating from slowQueryThreshold — the option was renamed to slowThreshold, and the per-entry isSlow boolean was removed. "Slow" is now the slow tag, computed centrally by the engine (no longer at capture time); read it from entry.tags or profile.tags.

Configuring severity

Each tag carries a severity ('info' | 'warning' | 'danger') that drives its colour everywhere in the UI — the pill, the duration text, the summary counts, the row highlight and the Performance banner. Every threshold-based tag's severity is configurable per collector, as a flat option next to its threshold:

// Treat a slow query as a hard failure in this app — the pill, duration, count and banner all turn red.
TypeOrmCollectorModule.forRoot({ slowThreshold: 50, slowSeverity: 'danger' });

The error tag is danger by default and is configurable like the others, but through its own option — what earns it is not a duration threshold but a definition of failure, which each package owns: ProfilerModule.forRoot({ error: { severity: 'warning' } }). See What counts as an error. A custom rule sets its own severity directly on the tag it emits (see below).

Filtering by tag

The list page shows a Performance tag select (Slow / N+1 / Chatty / Large payload / No rows) that keeps only the profiles carrying that tag, with the tag pills rendered inline on each row. Failures are not performance issues, so the error tag has its own Errors checkbox, alongside an Exception select that narrows to one failure type — see What counts as an error.

Custom rules

A rule inspects the collected entries and tags whatever it wants. Register one declaratively or programmatically:

import { PerformanceRule } from '@eleven-labs/nest-profiler';

const seqScanRule: PerformanceRule = {
  id: 'seq-scan',
  evaluate(ctx) {
    for (const { entries, domain } of ctx.collectors) {
      if (domain !== 'query') continue;
      for (const entry of entries) {
        if (/seq scan/i.test((entry as { sql?: string }).sql ?? '')) {
          ctx.tagEntry(entry, { id: 'seq-scan', label: 'Seq scan', severity: 'warning' });
        }
      }
    }
  },
};

ProfilerModule.forRoot({ performance: { rules: [seqScanRule] } });
// …or, from a module's onModuleInit: core.registerPerformanceRule(seqScanRule);

A rule's ctx.collectors entries carry duration, fingerprint and the concrete collector fields (cast by domain); call ctx.tagEntry(entry, tag) or ctx.tagProfile(tag). The emitted tag id becomes filterable — offer it in the list select with core.registerFilterOption('tag', { value: 'seq-scan', label: 'Seq scan' }).