Flagsmith/flagsmith

Race conditions are met with HTTP 500 by Core API

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#6617 opened on Jan 28, 2026

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 (5 comments) (0 reactions) (0 assignees)Python (3,475 stars) (264 forks)batch import
apigood first issue

Description

We're regularly seeing IntegrityError logs (example below) pop up, often because of poorly orchestrated scripts or racing frontend code.

We should come up with a unified approach to these. The expectation is that the backend should handle the conflicts opaquely, or clearly indicate to the client why the request couldn't go through. Options are: a) Consider wrapping mutating operations in transactions — unlikely outcome as we don't want to increase lock contention. b) Return 409 Conflict — a bit tricky as it'd take some heuristics to accurately detect race-related IntegrityErrors.

Sentry Issue: FLAGSMITH-API-5GY

UniqueViolation: duplicate key value violates unique constraint "lowercase_feature_name"
DETAIL:  Key (lower(name::text), project_id)=(pltn.objectbuilder.fixemptypagerace, 13318) already exists.

  File "django/db/backends/utils.py", line 89, in _execute
    return self.cursor.execute(sql, params)

IntegrityError: duplicate key value violates unique constraint "lowercase_feature_name"
DETAIL:  Key (lower(name::text), project_id)=(pltn.objectbuilder.fixemptypagerace, 13318) already exists.

(29 additional frame(s) were not displayed)
...
  File "features/views.py", line 270, in perform_create
    serializer.save(
  File "features/serializers.py", line 367, in create
    feature = super().create(validated_data)
  File "features/serializers.py", line 219, in create
    instance = super(CreateFeatureSerializer, self).create(validated_data)  # type: ignore[no-untyped-call]

Contributor guide

Tech stack
pythondjangopostgresql
Domain
backend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
Django ORMPostgreSQLConcurrency
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
45
Research direction
Explore the error in features/views.py line 270 and features/serializers.py line 367. Review the existing Sentry issue FLAGSMITH API 5GY for more context. Consider implementing a detection mechanism for IntegrityError that returns HTTP 409 Conflict, or explore alternative approaches like optimistic locking. Engage with the issue comments to clarify the preferred solution.