## Support semantics
This is a **candidate / unverified** Solution from the KFA Solution Factory Tier-2 gate. It is source-grounded research material, not an Outcome, and does **not** claim independent reproduction or confirmed field success.
## Cause
A timestamp alone is an incomplete sort key when duplicates exist; offset paging drifts under inserts and seek paging without a tie-breaker skips rows that share the delimiter value.
## Steps
1. Define ORDER BY columns that yield a deterministic sequence (extend with a unique id if needed).
2. Store the full last-seen tuple, not only the timestamp field.
3. Query with seek predicates (row-value or equivalent) using the stored tuple as the lower bound.
4. Add a fixture with many equal timestamps and assert the cursor advances through the entire cohort.
## Expected result
A dense equal-timestamp cohort drains completely; the persisted checkpoint unambiguously identifies the last consumed row.
## Misleading approaches
- Increasing LIMIT/OFFSET expecting stable progress under concurrent writes.
- Using only updated_at < ? when multiple rows share the same timestamp.
## Limitations
- Sources without a stable unique tie-breaker need a different checkpoint contract.
- Row-value seek syntax is not uniformly supported across databases.
- Not reproduced against a private pipeline in this run.
## Unknowns
- Best tie-breaker column when no primary key exists on the source.
## Evidence claims
- (documented_platform_behavior) Seek/keyset paging requires a deterministic ORDER BY; equal sort keys need an additional unique tie-breaker. — https://use-the-index-luke.com/sql/partial-results/fetch-next-page
- (documented_platform_behavior) Resuming with only the last timestamp delimiter can skip remaining rows that share that timestamp. — https://use-the-index-luke.com/sql/partial-results/fetch-next-page
- (documented_platform_behavior) DynamoDB encodes resumable position as LastEvaluatedKey passed forward as ExclusiveStartKey, not a single scalar timestamp alone. — https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Query.Pagination.html
Proposed approach
- Problem id
- 383425fa-6ed1-458d-bdef-390600ed04c3
- Proposed action
- Persist a composite cursor (ordered key columns plus a stable tie-breaker such as primary key) and page with seek/keyset predicates; prove dense-timestamp fixtures drain completely and the next run starts immediately after the last consumed tuple.
- Applicability
- State
- partial
- Text
- support: candidate_unverified (not an Outcome; no reproduction claim); Stateful consumers reading ordered changelogs or tables where many rows share the same event time or updated_at value.; fix_status: PARTIAL
- Limitations
- State
- partial
- Text
- Sources without a stable unique tie-breaker need a different checkpoint contract. Row-value seek syntax is not uniformly supported across databases. Not reproduced against a private pipeline in this run.
- Success criteria
- Not supplied
- Risk notes
- Not supplied
- Lifecycle
- active
Needs revalidation
LOW EVIDENCE
This exact knowledge revision needs ordinary execution evidence.
Useful environment or version
- State
- partial
- Text
- support: candidate_unverified (not an Outcome; no reproduction claim); Stateful consumers readin
Reported outcomes
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