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nextflow/docs/developer/nextflow.cache.md

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+
+# `nextflow.cache`
+
+The `nextflow.cache` package implements the cache database of previously executed tasks.
+
+## Class Diagram
+
+```{mermaid} diagrams/nextflow.cache.mmd
+```
+
+```{note}
+Some classes may be excluded from the above diagram for brevity.
+```
+
+## Notes
+
+The cache database uses [Kryo](https://github.com/EsotericSoftware/kryo) to serialize and deserialize task data. Each key-value pair in the cache database corresponds to a task. The key is the task hash, and the value consists of (1) the task `TraceRecord`, (2) the `TaskContext`, and (3) the task reference count.
+
+The default cache store is backed by [LevelDB](https://mvnrepository.com/artifact/org.iq80.leveldb/leveldb) and is stored in `.nextflow/cache/<session-id>` relative to the launch directory.
+
+The cloud cache store is backed by remote object storage such as Amazon S3, Azure Blob Storage, and Google Cloud Storage. It stores each task entry as a separate object.