percona/percona-server-mongodb
Nov 2024 – Mar 2026
16 Months active
Languages Used
C++JavaScriptYAMLIDLBSONPython
Technical Skills
Backend DevelopmentChange StreamsDatabase InternalsDistributed SystemsShardingTesting
Denis Grebennicov
PROFILE
Denis Grebennicov
Worked extensively on the percona/percona-server-mongodb repository, delivering robust backend features and test infrastructure for distributed MongoDB deployments. Focused on query settings, change streams, and sharding, this developer implemented persistent query shape storage, FCV-aware migrations, and advanced access control for representative queries. Leveraging C++, JavaScript, and Python, they enhanced test automation, resource management, and CI reliability, introducing features like pre-image truncation APIs and flexible historical placement retrieval. Their technical approach emphasized modular service design, rigorous test coverage, and safe upgrade paths, resulting in improved data integrity, operational safety, and maintainability for complex, high-concurrency database environments.
Overall Statistics
Feature vs Bugs
81%Features
Repository Contributions
58Total
Bugs
6
Commits
58
Features
25
Lines of code
25,903
Activity Months16
Your Network
596 peopleShared Repositories
247
Work History
March 2026
3 Commits • 2 Features
Mar 1, 2026March 2026 monthly summary focusing on delivering measurable business value: introduced key API and visibility improvements, and stabilized resource management to support high-concurrency workloads in the Percona MongoDB server project.
3 Commits • 2 Features
Mar 1, 2026March 2026 monthly summary focusing on delivering measurable business value: introduced key API and visibility improvements, and stabilized resource management to support high-concurrency workloads in the Percona MongoDB server project.
March 2026
February 2026
6 Commits • 2 Features
Feb 1, 2026February 2026: Delivered two core feature areas focused on test reliability/resource efficiency and data integrity in replicated environments. Implemented idle cursor detection hooks and improved test labeling to flag potential cursor leaks in concurrency tests, reducing flaky tests and guiding remediation. Introduced replicated pre-image truncation management including a new management class, a pre-image ID utility, and refined startup truncation logic with safeguards to preserve data integrity. These changes strengthen resource governance, test clarity, and replication-safe truncation across production-like workloads.
February 2026
6 Commits • 2 Features
Feb 1, 2026February 2026: Delivered two core feature areas focused on test reliability/resource efficiency and data integrity in replicated environments. Implemented idle cursor detection hooks and improved test labeling to flag potential cursor leaks in concurrency tests, reducing flaky tests and guiding remediation. Introduced replicated pre-image truncation management including a new management class, a pre-image ID utility, and refined startup truncation logic with safeguards to preserve data integrity. These changes strengthen resource governance, test clarity, and replication-safe truncation across production-like workloads.
January 2026
5 Commits • 1 Features
Jan 1, 2026Monthly summary for 2026-01 focusing on key features delivered, major bugs fixed, business value, and technical achievements for repository percona/percona-server-mongodb. Highlights include FCV upgrade/downgrade stability improvements and Timeseries change stream handling enhancements, with related commits. Deliverables and impact are described with respect to stability, correctness, and test coverage. Overview: - Repo: percona/percona-server-mongodb - Focus: FCV upgrade/downgrade stability, timeseries change stream enhancements, improved test coverage, and maintainability.
5 Commits • 1 Features
Jan 1, 2026Monthly summary for 2026-01 focusing on key features delivered, major bugs fixed, business value, and technical achievements for repository percona/percona-server-mongodb. Highlights include FCV upgrade/downgrade stability improvements and Timeseries change stream handling enhancements, with related commits. Deliverables and impact are described with respect to stability, correctness, and test coverage. Overview: - Repo: percona/percona-server-mongodb - Focus: FCV upgrade/downgrade stability, timeseries change stream enhancements, improved test coverage, and maintainability.
January 2026
December 2025
2 Commits • 1 Features
Dec 1, 2025Monthly summary for 2025-12: Delivered MongoDB Change Streams enhancements in percona/percona-server-mongodb, focusing on resilience and cross-shard routing. Implemented resumeToken reporting for change streams when batchSize is 0, enabling clients to resume watching changes even when no documents are returned in the initial batch. Introduced DatabaseChangeStreamShardTargeterImpl module to improve database-level change stream targeting and event routing across shards. These changes reduce downtime for streaming workloads and improve reliability in multi-shard deployments. Commits include 5aee2eb759f2d89799f189799222af755ea2362f and 1e029912d798c71220594aee4482da7878a2a8a6.
December 2025
2 Commits • 1 Features
Dec 1, 2025Monthly summary for 2025-12: Delivered MongoDB Change Streams enhancements in percona/percona-server-mongodb, focusing on resilience and cross-shard routing. Implemented resumeToken reporting for change streams when batchSize is 0, enabling clients to resume watching changes even when no documents are returned in the initial batch. Introduced DatabaseChangeStreamShardTargeterImpl module to improve database-level change stream targeting and event routing across shards. These changes reduce downtime for streaming workloads and improve reliability in multi-shard deployments. Commits include 5aee2eb759f2d89799f189799222af755ea2362f and 1e029912d798c71220594aee4482da7878a2a8a6.
November 2025
2 Commits • 1 Features
Nov 1, 2025Month 2025-11: Focused on strengthening test tooling for percona/percona-server-mongodb, delivering targeted improvements to enable safer debugging and expand Change Stream v2 validation. Key outcomes include: - New resmoke CLI option to disable hooks during test runs, simplifying debugging and reducing test noise; - Activation of pre-existing collection Change Stream v2 tests to verify compatibility with existing datasets and sharded configurations; - Refined testing workflow and tooling to reduce debugging time and increase confidence in Change Stream v2 readiness.
2 Commits • 1 Features
Nov 1, 2025Month 2025-11: Focused on strengthening test tooling for percona/percona-server-mongodb, delivering targeted improvements to enable safer debugging and expand Change Stream v2 validation. Key outcomes include: - New resmoke CLI option to disable hooks during test runs, simplifying debugging and reducing test noise; - Activation of pre-existing collection Change Stream v2 tests to verify compatibility with existing datasets and sharded configurations; - Refined testing workflow and tooling to reduce debugging time and increase confidence in Change Stream v2 readiness.
November 2025
October 2025
1 Commits • 1 Features
Oct 1, 2025October 2025: Delivered Change Stream Functionality Version 2 with a smoke test suite for sharded clusters in percona-server-mongodb. Implemented integration of system elements and smoke tests on a collection in Strict mode (commit fac2bb5f89131cca6b7a06ecd70d20fadf089ae1; SERVER-107442). This enhances production readiness, enables reliable real-time analytics across distributed deployments, and reduces upgrade risk. No major bugs fixed in this period; focus was on feature delivery, test automation, and traceability. Technologies/skills demonstrated include Change Streams V2, sharded clusters, smoke testing, Strict mode, Git-based traceability, and test automation.
October 2025
1 Commits • 1 Features
Oct 1, 2025October 2025: Delivered Change Stream Functionality Version 2 with a smoke test suite for sharded clusters in percona-server-mongodb. Implemented integration of system elements and smoke tests on a collection in Strict mode (commit fac2bb5f89131cca6b7a06ecd70d20fadf089ae1; SERVER-107442). This enhances production readiness, enables reliable real-time analytics across distributed deployments, and reduces upgrade risk. No major bugs fixed in this period; focus was on feature delivery, test automation, and traceability. Technologies/skills demonstrated include Change Streams V2, sharded clusters, smoke testing, Strict mode, Git-based traceability, and test automation.
September 2025
3 Commits • 2 Features
Sep 1, 2025September 2025: Focused on performance, observability, and flexibility in the MongoDB server code. Delivered QueryShapeHash enhancements to improve getMore logging and eliminate redundant hashing, and introduced a flexible historical placement retrieval mode to relax future-time checks in sharded data retrieval. These changes improve diagnostics, reduce CPU overhead, and broaden data access options for time-sensitive workloads. All work is traceable to specific tickets and commits.
3 Commits • 2 Features
Sep 1, 2025September 2025: Focused on performance, observability, and flexibility in the MongoDB server code. Delivered QueryShapeHash enhancements to improve getMore logging and eliminate redundant hashing, and introduced a flexible historical placement retrieval mode to relax future-time checks in sharded data retrieval. These changes improve diagnostics, reduce CPU overhead, and broaden data access options for time-sensitive workloads. All work is traceable to specific tickets and commits.
September 2025
July 2025
5 Commits • 2 Features
Jul 1, 2025July 2025 monthly summary for percona/percona-server-mongodb focusing on reliability, security, and feature completeness for representative queries and historical placement APIs. Delivered critical access control, bug fixes, and API enhancements that improve data integrity, operational safety, and planning for future times.
July 2025
5 Commits • 2 Features
Jul 1, 2025July 2025 monthly summary for percona/percona-server-mongodb focusing on reliability, security, and feature completeness for representative queries and historical placement APIs. Delivered critical access control, bug fixes, and API enhancements that improve data integrity, operational safety, and planning for future times.
June 2025
2 Commits • 1 Features
Jun 1, 2025June 2025: Delivered FCV-aware Query Settings Migration feature for Percona Server MongoDB, ensuring correct handling of representative query settings across FCV upgrade/downgrade transitions by migrating settings to a dedicated collection or back to cluster parameters. This work improves consistency and risk reduction during FCV state changes. Also expanded test coverage and alignment with FCV behavior through test-only adjustments.
2 Commits • 1 Features
Jun 1, 2025June 2025: Delivered FCV-aware Query Settings Migration feature for Percona Server MongoDB, ensuring correct handling of representative query settings across FCV upgrade/downgrade transitions by migrating settings to a dedicated collection or back to cluster parameters. This work improves consistency and risk reduction during FCV state changes. Also expanded test coverage and alignment with FCV behavior through test-only adjustments.
June 2025
May 2025
6 Commits • 1 Features
May 1, 2025In May 2025, delivered improvements to Query Settings for Percona Server MongoDB by centralizing the execution of setQuerySettings and removeQuerySettings on the config server and introducing persistent storage for query shape representative queries, integrated with the relevant commands and the $querySettings aggregation stage. Completed a refactor to simplify wiring by removing the setClusterParameterImpl-registerer and passing the setClusterParameter implementation directly to QuerySettingsService. Strengthened test infrastructure for multiversion reliability with more frequent cleanup, robust feature flag checks, and improved versioning controls (e.g., mongosBinVersion, isPresentAndEnabled checks). These efforts improve operational reliability across clusters, enable safer rollout of query settings features, and reduce flaky test behavior. Technologies demonstrated include distributed config server orchestration, collection-level persistence, aggregation pipelines, and advanced test automation.
May 2025
6 Commits • 1 Features
May 1, 2025In May 2025, delivered improvements to Query Settings for Percona Server MongoDB by centralizing the execution of setQuerySettings and removeQuerySettings on the config server and introducing persistent storage for query shape representative queries, integrated with the relevant commands and the $querySettings aggregation stage. Completed a refactor to simplify wiring by removing the setClusterParameterImpl-registerer and passing the setClusterParameter implementation directly to QuerySettingsService. Strengthened test infrastructure for multiversion reliability with more frequent cleanup, robust feature flag checks, and improved versioning controls (e.g., mongosBinVersion, isPresentAndEnabled checks). These efforts improve operational reliability across clusters, enable safer rollout of query settings features, and reduce flaky test behavior. Technologies demonstrated include distributed config server orchestration, collection-level persistence, aggregation pipelines, and advanced test automation.
April 2025
5 Commits • 3 Features
Apr 1, 2025April 2025 monthly summary for percona/percona-server-mongodb focused on strengthening the query settings pipeline and query shape handling across router and shard roles. Delivered three key features: modularization of QuerySettingsService for router and shard roles; API to update cluster-wide query settings via setQuerySettingsClusterParameter; and refactor of DocumentSourceQuerySettings into a proper DocumentSource. These changes improve modularity, enable cluster-wide configuration updates, and streamline query shape processing, aligning with long-term maintainability and reliability goals. No bugs fixed this month in the provided scope. Impact includes reduced maintenance complexity, clearer separation of concerns, and an improved foundation for future enhancements.
5 Commits • 3 Features
Apr 1, 2025April 2025 monthly summary for percona/percona-server-mongodb focused on strengthening the query settings pipeline and query shape handling across router and shard roles. Delivered three key features: modularization of QuerySettingsService for router and shard roles; API to update cluster-wide query settings via setQuerySettingsClusterParameter; and refactor of DocumentSourceQuerySettings into a proper DocumentSource. These changes improve modularity, enable cluster-wide configuration updates, and streamline query shape processing, aligning with long-term maintainability and reliability goals. No bugs fixed this month in the provided scope. Impact includes reduced maintenance complexity, clearer separation of concerns, and an improved foundation for future enhancements.
April 2025
March 2025
3 Commits • 1 Features
Mar 1, 20252025-03 Monthly Summary for percona/percona-server-mongodb: Focused on stabilizing test pipelines and expanding validation coverage for sharded deployments. Key work included stabilizing sharded concurrency tests by excluding problematic tests and aligning explain outputs to ensure consistent test behavior, and integrating the Query Shape Stability Fuzzer into the Evergreen CI pipeline to enable cross-node and cross-binary hash consistency checks. These efforts improve CI reliability, accelerate feedback, and strengthen the credibility of performance and correctness signals for sharded MongoDB workloads.
March 2025
3 Commits • 1 Features
Mar 1, 20252025-03 Monthly Summary for percona/percona-server-mongodb: Focused on stabilizing test pipelines and expanding validation coverage for sharded deployments. Key work included stabilizing sharded concurrency tests by excluding problematic tests and aligning explain outputs to ensure consistent test behavior, and integrating the Query Shape Stability Fuzzer into the Evergreen CI pipeline to enable cross-node and cross-binary hash consistency checks. These efforts improve CI reliability, accelerate feedback, and strengthen the credibility of performance and correctness signals for sharded MongoDB workloads.
February 2025
7 Commits • 2 Features
Feb 1, 2025February 2025 monthly summary for percona/percona-server-mongodb: consolidated query_settings management into a single service with improved robustness and stricter API coverage; expanded test suite reliability and observability for replication, multi-node reads, and plan-cache scenarios; and improved diagnostics through enhanced currentOp reporting and SBE plan-cache tagging in tests, enabling safer deployments and faster feedback cycles.
7 Commits • 2 Features
Feb 1, 2025February 2025 monthly summary for percona/percona-server-mongodb: consolidated query_settings management into a single service with improved robustness and stricter API coverage; expanded test suite reliability and observability for replication, multi-node reads, and plan-cache scenarios; and improved diagnostics through enhanced currentOp reporting and SBE plan-cache tagging in tests, enabling safer deployments and faster feedback cycles.
February 2025
January 2025
3 Commits • 3 Features
Jan 1, 2025In January 2025, the test infrastructure for percona/percona-server-mongodb was streamlined and hardened, delivering three focused contributions that improve reliability and velocity. Changes include simplifying Change Streams test configurations to remove an unnecessary parameter, tightening test resource lifecycle to prevent leaks via proper mongod shutdown, and modernizing the Query Shape system by introducing LetShapeComponent and removing CmdWithLetShape. These work items align with SERVER tickets SERVER-99163, SERVER-99292, and SERVER-99233, improving testing efficiency, stability, and architectural clarity. Overall impact: faster, more reliable test runs, easier maintenance, and clearer code paths in the test harness.
January 2025
3 Commits • 3 Features
Jan 1, 2025In January 2025, the test infrastructure for percona/percona-server-mongodb was streamlined and hardened, delivering three focused contributions that improve reliability and velocity. Changes include simplifying Change Streams test configurations to remove an unnecessary parameter, tightening test resource lifecycle to prevent leaks via proper mongod shutdown, and modernizing the Query Shape system by introducing LetShapeComponent and removing CmdWithLetShape. These work items align with SERVER tickets SERVER-99163, SERVER-99292, and SERVER-99233, improving testing efficiency, stability, and architectural clarity. Overall impact: faster, more reliable test runs, easier maintenance, and clearer code paths in the test harness.
December 2024
2 Commits • 1 Features
Dec 1, 2024December 2024: Delivered reliability improvements to the test suite for distributed MongoDB deployments in the percona/percona-server-mongodb repository. Implemented sharded-aware test utilities and ensured majority-commit semantics for secondary-read lookups, reducing flaky tests and improving data visibility guarantees in CI and production scenarios. These changes strengthen safety around sharded configurations and multi-document transactions, with clear synchronization points for last-operation commitment.
2 Commits • 1 Features
Dec 1, 2024December 2024: Delivered reliability improvements to the test suite for distributed MongoDB deployments in the percona/percona-server-mongodb repository. Implemented sharded-aware test utilities and ensured majority-commit semantics for secondary-read lookups, reducing flaky tests and improving data visibility guarantees in CI and production scenarios. These changes strengthen safety around sharded configurations and multi-document transactions, with clear synchronization points for last-operation commitment.
December 2024
November 2024
3 Commits • 1 Features
Nov 1, 2024November 2024 performance: Focused on enhancing data integrity in Change Streams and stabilizing test environments for the percona-server-mongodb repository. Delivered a new Change Stream parameter to validate collection UUIDs during update lookups and hardened tests to prevent unintended database drops during workload generation, improving reliability in both production behavior and CI workflows.
November 2024
3 Commits • 1 Features
Nov 1, 2024November 2024 performance: Focused on enhancing data integrity in Change Streams and stabilizing test environments for the percona-server-mongodb repository. Delivered a new Change Stream parameter to validate collection UUIDs during update lookups and hardened tests to prevent unintended database drops during workload generation, improving reliability in both production behavior and CI workflows.
Activity
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Quality Metrics
Correctness92.0%
Maintainability88.8%
Architecture90.6%
Performance84.0%
AI Usage22.8%
Skills & Technologies
Programming Languages
BSONC++IDLJavaScriptPythonYAML
Technical Skills
API DesignAPI developmentAccess ControlAggregation FrameworkBackend DevelopmentBuild System ConfigurationBuild System ManagementC++C++ DevelopmentC++ developmentC++ programmingCI/CDChange StreamsCode OrganizationCode Refactoring
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