ArcadeDB is a database management system that stores and works with several kinds of data, including graph, document, key-value, time-series, geospatial, and vector data. It is used by applications that need one database supporting interfaces such as SQL, Cypher, Gremlin, HTTP/JSON, MongoDB, and Redis. The catalogue add-on operates ArcadeDB.
Borrowing it
Nothing to install: this file belongs to ArcadeData/arcadedb. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/ArcadeData/arcadedb/main/.claude/skills/engine-concurrency/SKILL.mdgit clone --depth 1 https://github.com/ArcadeData/arcadedbWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/arcadedata/arcadedb/engine-concurrency)<a href="https://agentmods.dev/skills/arcadedata/arcadedb/engine-concurrency"><img src="https://agentmods.dev/badge/skills/arcadedata/arcadedb/engine-concurrency.svg" alt="Measured on agentmods" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00079 | $0.02883 |
| Opus 5 | $0.00039 | $0.01442 |
| Sonnet 5 | $0.00016 | $0.00577 |
| Haiku 4.5 | $0.00008 | $0.00288 |
Grade A, and why
engine-concurrency scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 7d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 117 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Engine Concurrency and Parallelism
Core principle: ArcadeDB avoids the JDK common ForkJoinPool (ForkJoinPool.commonPool()) for engine-internal parallelism. The common pool is shared with user-supplied code (Gremlin, Polyglot, custom SQL functions, application JVM) and JDK internals (parallel GC, reference handler), so long-running engine work submitted there starves user code and JDK housekeeping. Engine code that needs parallelism submits to one of the dedicated pools below; the rule is documented at the head of com.arcadedb.query.QueryEngineManager's class Javadoc.
Existing JDK-common-pool callers (tagged in source with NOTE (concurrency) comments referencing the rule, will migrate as workloads justify it):
GraphBatch.parallelSort(engine/...graph/GraphBatch.java)
ArcadeStateMachine.notifyInstallSnapshotFromLeader was on this list until issue #6202 gave it a dedicated
single-worker executor (arcadedb-raft-snapshot-install); a follower snapshot install is a full database
download, i.e. the longest-running thing the HA layer does, and it no longer parks a common-pool worker for it.
Dedicated thread pools
| Pool | Module | Purpose | Sizing | Saturation policy |
|---|---|---|---|---|
QueryEngineManager JVM-wide pool |
engine |
Query-time parallelism: graph algorithms (parallelForRange), parallel index scans, anything that forks query work |
arcadedb.queryParallelismPoolThreads (default max(2, CPU)) |
Bounded queue (arcadedb.queryParallelismQueueSize, default 1024), caller-runs rejection, throttled WARNING (60s window) |
SparseVectorScoringPool |
engine |
Reserved for per-segment parallel scoring of LSM_SPARSE_VECTOR top-K (dispatch wiring deferred to issue #4085) |
arcadedb.sparseVectorScoringPoolThreads (default max(2, CPU)), 1024 queue; lazy-init via Holder idiom |
Bounded queue, caller-runs, throttled WARNING |
ParallelScanProducerPool |
engine |
The BLOCKING producer tasks of a parallel bucket scan (FetchFromTypeExecutionStep.syncPullParallel) |
arcadedb.parallelScanProducerPoolThreads (default max(2, CPU)) |
Deviation: unbounded queue and NO caller-runs - caller-runs on a blocking producer is the #4948 self-deadlock. Back-pressure comes from each query's bounded RESULT queue; queue_depth is the saturation signal |
AsyncCommandPool |
engine |
Commands dispatched with awaitResponse=false that parse to DDL, which cannot run on an async worker (#6303 item 3) |
arcadedb.asyncCommandPoolThreads (default max(2, CPU)), arcadedb.asyncCommandQueueSize (default 1024) |
Bounded queue, caller-runs even on a shut-down pool (there is no future to cancel and the submitter has already counted the command as in flight), throttled WARNING |
DatabaseAsyncExecutor |
engine |
Per-database async ops (background scheduled tasks, async commit) | arcadedb.asyncWorkerThreads (default CPU - 1, min 1) |
Bounded queue (arcadedb.asyncOperationsQueueSize, default 1024) |
PageManagerFlushThread |
engine |
Dedicated single thread for paginated-component page writes | 1 thread | Backpressure via arcadedb.maxRAMForPageRamUsageInMB |
TransactionManager Timer |
engine |
Periodic WAL housekeeping | Timer thread | n/a |
TimeSeriesEngine pool |
engine |
Time-series rollup work | configurable | n/a |
BackupScheduler |
server |
Cron-style backup jobs | scheduled executor | n/a |
MaterializedViewScheduler |
server |
Cron-style MV refresh | scheduled executor | n/a |
| Raft HA pools | ha-raft |
Leader election, log replication | configurable in Raft conf | n/a |
ArcadeStateMachine.snapshotInstallExecutor |
ha-raft |
Leader-initiated follower snapshot install, off the Ratis state-machine thread | 1 worker, 16-deep queue (Ratis serialises installs per division) | Abort, turned into a failed future so Ratis retries - never caller-runs, which would put the download back on the Ratis thread |
| Undertow IO + worker | server |
HTTP request handling | hardcoded 500 worker threads | Undertow built-in |
ServerMonitor |
server |
Periodic metric collection | scheduled executor | n/a |
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 7d ago First seen · 117 lines · 79 tokens per session scan A 8ab88048bda2
engine-concurrency is a skill published in the GitHub repository ArcadeData/arcadedb (1,130 stars, last pushed today), licensed Apache-2.0. It adds 79 tokens to every session and 2,883 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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