Variable: EventKeyDefinition

const EventKeyDefinition: z.ZodObject<{
  backfilledAt: z.ZodOptional<z.ZodNullable<z.ZodCoercedDate<unknown>>>;
  createdAt: z.ZodCoercedDate<unknown>;
  createdBy: z.ZodOptional<z.ZodNullable<z.ZodString>>;
  id: z.ZodGUID;
  linkSubjects: z.ZodBoolean;
  name: z.ZodString;
  normalize: z.ZodEnum<{
     lowercase: "lowercase";
     none: "none";
  }>;
  path: z.ZodString;
  status: z.ZodEnum<{
     active: "active";
     backfilling: "backfilling";
  }>;
  tenantId: z.ZodGUID;
  updatedAt: z.ZodCoercedDate<unknown>;
}, z.core.$strip>;

A tenant's own key velocity rules group by (groupBy: 'key'), beside the subject and the promoted keys: a value in each event's attributes (path), indexed per event so a count over it is one range read. linkSubjects makes subjects whose events share a value linked (GET /subjects/:id/links). path and normalize are fixed once created.