Designs by Duhart ← All infographics

Designs by Duhart · /srv work inventory

Twenty-eight projects, ranked for one job

Distributed Systems Engineer — Google / Spotify / financial institution. Every project in /srv scored against what those loops actually test, not against how impressive it looks.

28projects inventoried
~4.3Mlines authored
13backend services
10edge Workers
4datastore families
3client platforms

The rubric — weight × rating, max 120

Canonical DS primitives ×5Partitioning, event logs, idempotency, fan-out, backpressure
Production evidence ×4Deployed, measured, runbooked, failure modes named
Concurrency correctness ×4Races found, fixed, and tested for
Scale artifacts ×3Shard keys, consumer groups, TTLs, hot keys
Language fit ×3Go, Java, Python, C++
Contract discipline ×2OpenAPI / AsyncAPI / protobuf, CI-enforced
Written communication ×2Design docs stating trade-offs and costs
Frontend / mobile ×1Real work; not what this role hires on

Tier S · 95+

Lead with these. They are the interview.

1
Billboard Activity GraphOutbox → Kafka → three consumer groups → Cassandra + Postgres + realtime · app/BillboardActivityService
103of 120
2
GlobalChat Realtime Messaging26K-line Go service on Cassandra, Redis, Kafka, WebSocket · app/GlobalChatService
106of 120
3
Match Service — Distributed RankingGeo-partitioned Cassandra + Redis Streams; two production defects fixed · app/MatchService
101of 120
The top three sit within 5 points of 120 — that is noise, not a measurement. GlobalChat edges the rubric on production evidence and breadth. The Activity Graph is listed first anyway because it leads on the axis that decides a systems-design round: it is the canonical question, with every trade-off already written down. Open with it; bring GlobalChat as proof you have carried something this size in production.

Tier A · 75–94

Strong support — infrastructure, ML platform, media.

4
Solomon — Serving, Kubernetes & AutoscalingSSE/WS streaming, continuous batching, k3s + Helm + HPA to 3 replicas · Solomon/k8s
90of 120
5
Solomon — LLM Platform (umbrella)The whole pipeline; decomposes into six projects · Solomon/
89of 120
6
Billboard Production HardeningForgeable auth → RS256 four-tier; 60 commits against a gap register · app/workers/billboard_users
84of 120
7
WebRTC Calling PlaneICE/STUN/TURN, P2P vs orphaned SFU, a fatal map race located · docs/webrtc-chat/
83of 120
8
Media & Upload InfrastructureR2 multipart across five modes, IngestDO single-writer sessions, TUS · app/GlobalCloudflareAdapter
80of 120
9
Push & Notification PipelineKafka → consumer → APNs + PushKit VoIP; dedupe as a user-visible concern · app/GlobalChatService
79of 120
10
Solomon — Retrieval & Agent Tier4,757 lines of Go: index, bounded agent loop, grounding guard under test · Solomon/retrieval
75of 120

Tier B · 60–74

Real systems work, narrower interview surface.

11
Platform Operations & CI/CDsystemd incl. a restore-verify timer; CI gates that encode past defects · deploy/ .github/
73of 120
12
Auth & Identity PlatformgRPC/Connect, RS256 issuance, ACL, 24 protobufs → Go + Swift + TS · app/AuthGateway
70of 120
13
GlobalChat Messaging UItransport/store/runtime split; a wiring record that retracts itself · IOS/…/GlobalChat
70of 120
14
Realtime Gateway Trio48K lines of Go: connection / session / presence, three times · app/gateways/
69of 120
15
Cloudflare Edge Platform10 Workers over D1, R2, KV, Durable Objects, Hyperdrive; WASM FFT in a DO · app/workers/
68of 120
16
Solomon — Evaluation Gates & PromotionNine release-blocking gates, two of them latency and throughput · Solomon/solomon/evaluation
65of 120
17
Solomon — Training & Experiment TrackingNoam + label smoothing, MLflow, SHA256 run manifests, val PPL 40.0 · Solomon/solomon/training
63of 120
18
Dating Swipe Deck & Discovery UIThe largest mode — and where the phantom partition became visible · IOS/TheOne/Dating
62of 120
19
BoxOffice & the Moderator Console“27 endpoints and curl” → an operator console for statutory deadlines · IOS/…/BoxOffice
61of 120

Tier C · under 60

Breadth and depth-of-craft. Mention, don’t lead.

20
OpenHouse Global7 forward-only CQL migrations; buyer journey as a state machine · app/OpenHouseGlobal
57of 120
21
Billboard Player — Audio UI & EngineAVPlayer behind an actor, audio tap, live spectrum, vDSP FFT fingerprints · IOS/TheOne/Billboard
56of 120
22
Palantir J8 — Exhibit FactoryOntology-driven financial pipeline; fail-closed ingest · Palantir/J8
55of 120
23
Multiplatform Clients (umbrella)611K lines Swift / 13 modes; decomposes into five UI projects · IOS/ Android/
54of 120
24
Solomon — The TransformerBuilt from the paper, deviations justified; KV cache proven equivalent · Solomon/solomon/model
53of 120
25
Web Platform UIEvery mode in one Next.js app, compiled against the backend’s protobufs · app/web-platform
51of 120
26
Solomon — Corpus, Tokenizer & Data Governance130M tokens deduped, BPE with 0 UNK, data card with contamination checks · Solomon/solomon/data
46of 120
27
Technical Documentation CorpusThree 17–20 chapter manuals with gap registers; 14/52 Spotify parity · docs/
39of 120
28
Portfolio & Marketing InfrastructureCloudflare Pages; a DNS plan whose step 2 saves your email · Portfolio/
17of 120
Two entries are umbrellas and are not double-counted. Solomon — LLM Platform (rank 5) decomposes into ranks 4, 10, 16, 17, 24 and 26. Multiplatform Clients (rank 23) decomposes into ranks 13, 18, 19, 21 and 25 — the five user-interface projects.
Table view — all 28 by score
RankProjectTierScore / 120
2GlobalChat Realtime MessagingTier S106
1Billboard Activity GraphTier S103
3Match Service — Distributed RankingTier S101
4Solomon — Serving, Kubernetes & AutoscalingTier A90
5Solomon — LLM Platform (umbrella)Tier A89
6Billboard Production HardeningTier A84
7WebRTC Calling PlaneTier A83
8Media & Upload InfrastructureTier A80
9Push & Notification PipelineTier A79
10Solomon — Retrieval & Agent TierTier A75
11Platform Operations & CI/CDTier B73
12Auth & Identity PlatformTier B70
13GlobalChat Messaging UITier B70
14Realtime Gateway TrioTier B69
15Cloudflare Edge PlatformTier B68
16Solomon — Evaluation Gates & PromotionTier B65
17Solomon — Training & Experiment TrackingTier B63
18Dating Swipe Deck & Discovery UITier B62
19BoxOffice & the Moderator ConsoleTier B61
20OpenHouse GlobalTier C57
21Billboard Player — Audio UI & EngineTier C56
22Palantir J8 — Exhibit FactoryTier C55
23Multiplatform Clients (umbrella)Tier C54
24Solomon — The TransformerTier C53
25Web Platform UITier C51
26Solomon — Corpus, Tokenizer & Data GovernanceTier C46
27Technical Documentation CorpusTier C39
28Portfolio & Marketing InfrastructureTier C17