📄 api/services/billing_service.py:292

On line 292, when validation fails for a tenant's plan data, the code sets results[tenant_id] = None. This contradicts the intended behavior (skip invalid tenants) and has two downstream consequences:

1. Test failure: The unit test test_get_plan_bulk_with_invalid_tenant_plan_skipped asserts "tenant-invalid" not in result and len(result) == 2, but the code adds the invalid tenant with value None, so len(result) will be 3 and the assertion will fail.

2. Type violation: get_plan_bulk is typed as returning dict[str, SubscriptionPlan], but it returns None values. This propagates into get_plan_bulk_with_cache which will add None to tenant_plans, cache "null" in Redis (via json.dumps(None)), and on the next cache read, validate_python(None) will fail, causing a perpetual miss-refetch-cache cycle for that tenant.

The fix is to use continue instead of assigning None.

                    except Exception:
                        logger.exception(
                            "get_plan_bulk: failed to validate subscription plan for tenant(%s)", tenant_id
                        )
                        continue

📄 api/services/billing_service.py:365

Since get_plan_bulk currently sets results[tenant_id] = None for validation failures (line 292), get_plan_bulk_with_cache will blindly iterate over these None entries at line 365-367, adding them to both tenant_plans (returned to the caller) and plans_to_cache. Then json.dumps(None) produces "null", which gets cached in Redis. On the next cache read, json.loads("null") returns None, and validate_python(None) will fail, treating it as a cache miss — causing a repeated cache-miss → fetch → cache-"null" cycle.

This is a direct consequence of the line 292 bug. Once line 292 is fixed to continue instead of assigning None, this issue is also resolved. However, as a defensive measure, you could also add a None check in the caching loop:

for tenant_id, subscription_plan in bulk_plans.items():
    if subscription_plan is not None:
        tenant_plans[tenant_id] = subscription_plan
        plans_to_cache[tenant_id] = subscription_plan