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Atlassian

Atlassian Engineering blog (atlassian.com/blog/how-we-build). Tier-3 source on the sysdesign-wiki. Much of the blog is product-marketing / feature-announcement content for Jira / Confluence / Bitbucket / Rovo — which is filtered out on ingest (see wiki/log.md). When the blog does go architectural, four axes are in scope:

  • Confluence's web-tier performance — React-18 streaming SSR, hydration semantics, edge-proxy buffer-kill; 2026-04-16 streaming-SSR post is the canonical wiki instance.
  • Rovo Chat's agent orchestration architecture (Long Horizon) — single-LLM iterative reasoning loop replacing a hierarchical multi-agent orchestrator; flattened tool surface with progressive disclosure via meta-tools; context compaction service; prompt layer ordering for prefix-cache maximisation; child instances for parallel research; adaptive reasoning effort. The 2026-06-18 "Long Horizon" post is the canonical wiki instance.
  • Atlassian's ML platform (ML Studio) — unified enterprise-scale ML development platform with composable versioned modules, workflow orchestrator (hot clusters, deterministic caching, nested workflows), and embedded multi-layer compliance (column-level data classification with automatic tag propagation); serves ~120k monthly workflow runs across 100+ ML teams and is the backbone for Rovo Search/Chat, Teamwork Graph, and Confluence AI. The 2026-06-10 ML-platform-architecture post is the canonical wiki instance.
  • Atlassian's agentic-AI platform / Rovo Dev ecosystem — Fireworks (the Firecracker-microVM-on-Kubernetes secure execution substrate for AI agents), the Rovo Dev agent itself, Bitbucket Pipelines as automated quality gate for agent PRs, and the agentic-development workflow Atlassian runs internally (dev-shard iteration, AI-written e2e tests, adversarial-review sub-agents, orchestration meta-skills). The 2026-04-24 Rovo-Dev-Driven-Development post is the canonical wiki instance.
  • Developer-productivity / CI-reliability at Atlassian-repo scaleBitbucket Merge Queues defending against semantic merge conflicts at Jira-repo scale (800+ devs, 300+ merges/day, 70+ repos, 30,000+ PRs landed through merge queues). 2026-04-29 merge-queue architecture + outcomes post is the canonical wiki instance.
  • Jira Cloud multi-tenant configuration scalingJira Optimisation Tools paired with Site Optimiser and the Pre-computation Framework address configuration bloat at Atlassian-tenant-scale (100k+ users per tenant). The 2026-05-14 "Optimisation Tools for Jira" post is the canonical wiki instance, contributing the polymorphic usage tables decision (rejecting per-entity-type tables to avoid "millions of tables across production"), the Initialise → Scan-steps → Finalise batch-framework contract with idempotent + thread-safe + order-agnostic scan-step workers, the utilisation-prioritised refresh strategy (recompute only spaces near ≈70% of cap), the tiered Memcache + DB storage split, and the audit-log-as-rollback v1 contract.
  • Jira-as-substrate for AI-agent KTLO automation — the Atlassian Jira engineering team uses Jira's structured custom fields, workflow state machine, and workflow-transition automations as the substrate for delegating KTLO engineering chores to AI agents (likely Rovo Dev). The 2026-06-01 "How We Cut up to 80% of Engineering Chores Using AI Agents in Jira" post is the canonical wiki instance, contributing the work-item-as-agent-prompt framing, the status- transition-triggers-agent-with-custom-system-prompt mechanic, the daily-heuristic- cron-emits-agent-ready-work-items detection layer, the three-tier repo-specific → flag-for-creation → generic skill fallback chain, the per-test-category classify-then-dispatch mechanism, and the [first-pass-investigator
  • human-merge-gate](<../concepts/agent-as-first-pass-investigator.md>) operational model. Reported outcomes: ~80% reduction in flaky-test eng hours (~1 engineering week saved per month); 500+ merged PRs in 70 days from stale-flag cleanup on the Jira repo. Composes load-bearingly with the Bitbucket-merge-queue substrate (systems/bitbucket-merge-queues) for the cleanup-throughput economics.

Key systems

  • systems/atlassian-long-horizon — Atlassian's reasoning-native agent orchestrator powering Rovo Chat. Single LLM, single context, up to 150-iteration reasoning loop. Replaced the hierarchical Hybrid Orchestrator. Flattened tool surface + progressive disclosure + context compaction + child instances + prompt layer ordering for prefix caching + adaptive reasoning.
  • systems/rovo-chat — Atlassian's user-facing AI assistant product; cross-product research and actions across Jira, Confluence, Bitbucket, JSM, Compass, and third-party connectors. Powered by Long Horizon.
  • systems/atlassian-ml-studio — Atlassian's unified enterprise-scale ML development platform; three architectural pillars (composable versioned modules, workflow orchestrator with hot clusters + deterministic caching, embedded multi-layer compliance); serves ~120k monthly workflow runs across 100+ ML teams; backbone for Rovo Search/Chat, Teamwork Graph, Confluence AI.
  • systems/atlassian-jira-optimisation-tools — admin experiences + async backend workflows that compute per-space configuration-usage reports and apply bulk remediation actions (dissociate unused fields, split field configuration schemes, clean up unused work types). Powers Jira's response to the post-100k-user configuration-bloat problem.
  • systems/atlassian-jira-site-optimiser — admin dashboard surface that surfaces "configuration issues and improvement opportunities across spaces"; the human-facing entry point to the Optimisation Tools.
  • systems/atlassian-precomputation-framework — async batch-reporting platform on Atlassian's internal workflow orchestration engine; Initialise → Scan-steps → Finalise three-phase contract; idempotent + thread-safe
  • order-agnostic scan-step worker discipline; tiered Memcache + relational-DB storage with polymorphic usage tables. Canonical first-party wiki instance of patterns/asynchronous-precomputed-report-batch-framework.
  • systems/jira — host system / multi-tenant SaaS; recently extended for Jira Cloud limits + guardrails + optimisation-tools coverage; also the substrate for AI-agent KTLO automation via custom-fields + workflow-transition agent integration.
  • systems/atlassian-teamwork-graph — Atlassian's cross-product knowledge graph (Jira + Confluence + Bitbucket
  • …); named in the 2026-06-01 KTLO-AI-agents post as one of the three context substrates the agent reads (alongside the work item itself and the workflow-automation system prompt). Stub page; deeper architectural decomposition deferred to a future ingest.
  • systems/atlassian-fireworks — Firecracker-microVM orchestrator on Kubernetes; the "secure execution engine behind Atlassian's AI agent infrastructure." 100ms warm starts, live migration, eBPF network policy, shared volumes, snapshot filesystem restore, sidecar sandboxes; internal scheduler + autoscaler + Raft persistence + Envoy ingress. "Built in four weeks, entirely by LLMs."
  • systems/rovo-dev — Atlassian's AI development agent; deep Bitbucket + Bitbucket Pipelines integration; supports addressable skills (including multi-step orchestration meta-skills), prompt shortcuts like !review-pr for adversarial sub-agent review, and PR-bot participation on the PR itself.
  • systems/bitbucket-pipelines — Atlassian's CI/CD product; serves both as the automated quality gate Rovo Dev reads pipeline output from and as the execution substrate for the merge-queue pipeline (via the merge-queues: section in bitbucket-pipelines.yml).
  • systems/bitbucket-merge-queues — Atlassian's pre-merge validation queue for Bitbucket Cloud. 70+ repos in production across Jira, Rovo, Trello; 30,000+ PRs landed via merge queues since Beta; canonical first-party validate-against- future-state-of-main instance on the wiki.
  • systems/bitbucket — host of the repo, PRs, merge-queue admin surface, and Rovo Dev's operating surface.
  • systems/confluence-streaming-ssr — Confluence's React-18 streaming SSR pipeline; renderToPipeableStream + Suspense + NodeJS-transform state injection; ~40% FCP win.

Key patterns / concepts

Rovo Chat Long Horizon architecture (2026-06-18 axis)

Jira-as-substrate for AI-agent KTLO automation (2026-06-01 axis)

  • concepts/ktlo-engineering-chores — first-class wiki home for the "keeping the lights on" work-category framing. Atlassian names the canonical KTLO category list (flag cleanup, flaky tests, vulnerabilities, a11y fixes, long-tail bugs) and the pattern-recognition prerequisite argument for delegation: "That pattern recognition is what makes delegation to agents possible."
  • concepts/work-item-as-agent-prompt — Jira work item treated as a structured agent prompt; structured custom fields carry per-task brief; workflow state machine is the orchestration layer; transition automation carries the per-procedure system prompt; cross-product Teamwork Graph supplements with shared cross-task context.
  • concepts/agent-as-first-pass-investigator — operational model: agent does investigation + diagnosis + draft PR; human reviews + merges; "hours of manual investigation can now become minutes of review." Triage-vs-fix split with bounded false-positive comment-only exit.
  • patterns/jira-status-transition-triggers-agent-workflow — Jira-Cloud-native mechanic: status change triggers agent run with custom system prompt encoded into the transition automation. Single-source-of-truth lifecycle preserved on the work item.
  • patterns/heuristic-cron-emits-agent-work-items — daily cron scans codebase + cross-references compliance / experiment / release-track state, emits one Jira work item per stale flag with full pre-resolved structured fields (flag name + type + repo + paths + line numbers + desired final state). Detection layer for the agentic remediation pipeline.
  • patterns/agent-skill-with-fallback-chain — three-tier fallback for per-codebase variability: repo-specific cleanup skill → flag the repo as needing one + provide owner instructions → generic cleanup skill. The middle tier converts "no skill exists" into operational signal.
  • patterns/test-category-classifier-then-specialist-skill — for flaky-test triage / fix: classify the test as unit / integration / visual regression, dispatch to the matching specialist skill. CPU-throttled-loop reproduction discipline. Sibling skill-dispatch axis to the per-codebase fallback chain.
  • Reported outcomes: ~80% reduction in flaky-test eng hours (~1 engineering week saved per month); 500+ merged PRs in 70 days from stale-flag cleanup on the Jira repo alone.

Jira Cloud multi-tenant configuration scaling (2026-05-14 axis)

Agentic development (2026-04-24 Fireworks axis)

Web-tier performance (2026-04-16 Confluence axis)

Developer-productivity / CI-reliability (2026-04-29 Bitbucket Merge Queues axis)

Recent articles

Skipped (logged)

  • 2026-06-01 — The AI-native SDLC is paying off: 19% more PRs and 2-3 hours saved per developer per week (Tier-3 Rovo Dev productivity-measurement marketing post; quasi-experimental statistics on 3,400 repos + 6,200-developer survey; no distributed-systems internals, no scaling trade-offs, no infrastructure architecture, no production incidents — body is ~50% measurement framework + statistics tables, ~30% outcome tables, ~20% explicit Rovo Dev rollout-recommendation product pitch)
  • 2026-06-01 — From alert noise to action: how 24 Hour Fitness transformed IT Ops with JSM (Tier-3 customer-case-study product PR for Atlassian Service Collection)
  • 2026-05-14 — Inside Reddit's IT playbook: Building for scale and AI-readiness (Atlassian customer-success / webinar-recap; corporate IT modernization narrative + product pitch, zero architectural content)
  • 2026-05-13 — 3 ways AI alert grouping is transforming on-call engineering (Jira Service Management AIOps product PR; listicle format)
  • 2026-04-16 — Enhancing Developer Workflow with Rovo Dev and Notifications (product PR)
  • 2026-04-16 — Merge Queues for Bitbucket Cloud, now in open beta (product PR — superseded by the 2026-04-29 first-party architectural follow-up which is ingested as sources/2026-04-29-atlassian-inside-atlassians-merge-queues)
  • 2026-04-16 — Rovo Dev in Frontend Platform Engineering (AI-agent codemod tooling)
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