Fictional resume example. Names, employment histories and results are illustrative, not an actual employee record.
Mark Foster
Backend engineer with PostHog and Datadog experience in event ingestion and log processing. Designs Kafka-backed pipelines, tenant isolation and recovery tests, connecting latency and throughput improvements to durable event delivery.
Experience
PostHog
Remote (EMEA) · United Kingdom
Software Engineer
Mar 2022 - now
- Built a Go ingestion worker that batches Kafka events into PostgreSQL, with idempotency keys and a replay test that caught duplicate writes after a timeout.
- Tested distributed systems reliability by stopping a consumer during replay; bounded Redis deduplication keys and queue backpressure kept recovery from exhausting memory.
- Reworked a Rust capture handler using benchmarking and profiling on a fixed 20,000-event/s replay. Bounded decompression and moved validation before allocation, reducing p95 acknowledgment latency from 180 ms to 112 ms without acknowledging events before Kafka persistence.
- Designed multi-tenant queue limits keyed by project and distinct ID. Isolated one high-volume client in an overflow lane, then checked data integrity against Kafka offsets and PostgreSQL identity mappings; healthy tenants retained their latency target during a 3× traffic spike.
- Built observability around consumer lag, retry volume and end-to-end ingestion delay. During an on-call incident, traced a stalled partition to a poison event, replayed the quarantined batch and reconciled event counts before closing the incident; added the reproducer to the canary release gate.
- Added Kafka consumer-lag and dead-letter alerts with tenant identifiers; linked each alert to replay commands and verified that a repeated event did not create a second record.
- Owned a Kafka ingestion replay test using tenant-isolated fixtures, resolving duplicate PostgreSQL writes without changing the ordering contract for other tenants.
- Released a Go benchmark harness for the ingestion path and profiled allocation hotspots, reducing peak memory by 21% on the same captured workload.
Datadog
London · United Kingdom
Software Engineer
Jan 2019 - Feb 2022
- Implemented schema validation in the Node.js producer before events reached the Go worker. Replayed incompatible payloads in a contract test and prevented malformed events from entering Kafka while preserving the failed request for diagnosis.
- At Datadog, implemented Go workers for a log-processing service and bounded Redis deduplication keys by customer and retry window. Replayed 2 million synthetic records with duplicated requests; PostgreSQL reconciliation found no missing accepted records after worker restarts.
- Migrated 36 PostgreSQL tables with expand-contract changes and a rehearsed rollback. Separated schema deployment from application rollout and verified old and new writers against the same fixtures; completed the change without stopping customer writes.
GoCardless
London · United Kingdom
Software Engineer
Jul 2017 - Dec 2018
- At a payments software team, added contract tests for webhook signatures, repeated delivery and out-of-order events. Replaced manual release checks with replayable fixtures, catching a retry regression before the next customer integration shipped.
Selected project
Event replay and recovery testbed
London, United Kingdom
Design and implementation
Feb 2024 - Jun 2024
- Built a local event-replay harness with synthetic tenant traffic, a controllable Kafka outage and an S3 archive. Measured recovery time and checked unique-event counts before and after replay, making data-loss and duplicate-delivery failures reproducible in CI.
- Published the fixture generator, benchmark settings and failure matrix in the project report. Compared strict ordering with overflow isolation and recorded which consumer assumptions must change before either design can be deployed.
- Owned the independent regression fixture using isolated inputs, resolved a failing edge case and released a reproducible test package with expected outputs.
Education
University of Manchester
Manchester · United Kingdom
B.Sc. Computer Science
Sep 2014 - Jun 2017
Relevant coursework: Algorithms, operating systems, databases, computer networks
Skills
Languages and storage
Rust · Node.js · Go · Kafka · PostgreSQL · Redis
Systems work
Tenant isolation · Data integrity · Observability
Delivery and review
Load testing · Regression tests · Incident recovery
Publications
- Published an independent technical note using the project’s before-and-after traces, explaining the failed assumption, regression coverage and cases the implementation does not support.


