Backends¶

ExpOps supports multiple backends for caching and storage.

Cache Backends¶

Local Filesystem¶

Default backend for local development:

model:
  parameters:
    cache:
      backend: local

Features:

Fast access
No external dependencies
Limited to single machine
No web UI metrics support

Caching Limitation: When using the default in-memory KV backend, caching only works within a single process execution. The cache metadata (which tracks where cached results are stored) is lost when the process restarts, so cached results cannot be retrieved across runs even if the cache files exist on disk. For persistent caching across runs, you must configure a persistent KV backend (see KV Backends below).

Google Cloud Storage (GCS)¶

Remote backend for shared caching:

model:
  parameters:
    cache:
      backend: gcs
      bucket: my-bucket

Features:

Cross-machine sharing
Persistent storage
Web UI support
Requires GCP credentials

Setup:

Create GCS bucket
Set up credentials in keys/
Configure bucket name in config

Custom Backends¶

Implement custom backends for other storage systems.

KV Backends¶

Key-value backends for metrics, metadata, and cache indexing:

The KV backend stores cache metadata (indexes that track where cached results are located). This is separate from the cache backend which stores the actual cached data files.

Default: If not specified, the system uses an in-memory KV store which is not persistent. This means:

Cache metadata is lost when the process restarts
Caching only works within a single process execution
Cached results cannot be retrieved across runs

For persistent caching across runs, configure a persistent KV backend (Firestore).

Firestore¶

Google Cloud Firestore:

model:
  parameters:
    cache:
      backend: gcs
      kv_backend: firestore

Features:

Persistent cache metadata
Enables caching across runs
Web UI metrics support
Requires GCP credentials

Setup:

Create Firestore database
Add credentials to keys/firestore.json
Configure in project config

Configuration¶

Backend settings in configs/project_config.yaml:

model:
  parameters:
    cache:
      backend: gcs  # or local, custom
      bucket: my-bucket  # for GCS
      kv_backend: firestore  # optional: firestore, redis, or memory (default, not persistent)

Note: The kv_backend setting controls where cache metadata is stored. For persistent caching across runs, use firestore. The default memory backend only works within a single process execution.

Web UI Requirements¶

For web UI metrics and charts: - Use remote backend (GCS, etc.) - Configure KV backend for metrics - Ensure credentials are set up