feat: Qdrant skills (#1412)

skills/qdrant-scaling/scaling-data-volume/sliding-time-window/SKILL.md

@@ -0,0 +1,68 @@
+---
+name: qdrant-sliding-time-window
+description: "Guides sliding time window scaling in Qdrant. Use when someone asks 'only recent data matters', 'how to expire old vectors', 'time-based data rotation', 'delete old data efficiently', 'social media feed search', 'news search', 'log search with retention', or 'how to keep only last N months of data'."
+---
+
+# Scaling with a Sliding Time Window
+
+Use when only recent data needs fast search -- social media posts, news articles, support tickets, logs, job listings. Old data either becomes irrelevant or can tolerate slower access.
+
+Three strategies: **shard rotation** (recommended), **collection rotation** (when per-period config differs), and **filter-and-delete** (simplest, for continuous cleanup).
+
+
+## Shard Rotation (Recommended)
+
+Use when: data has natural time boundaries (daily, weekly, monthly). Preferred because queries span all time periods in one request without application-level fan-out. [User-defined sharding](https://search.qdrant.tech/md/documentation/operations/distributed_deployment/?s=user-defined-sharding)
+
+1. Create a collection with user-defined sharding enabled
+2. Create one shard key per time period (e.g., `2025-01`, `2025-02`, ..., `2025-06`)
+3. Ingest data into the current period's shard key
+4. When a new period starts, create a new shard key and redirect writes
+5. Delete the oldest shard key outside the retention window
+
+- Deleting a shard key reclaims all resources instantly (no fragmentation, no optimizer overhead)
+- Pre-create the next period's shard key before rotation to avoid write disruption
+- Use `shard_key_selector` at query time to search only specific periods for efficiency
+- Shard keys can be placed on specific nodes for hot/cold tiering
+
+
+## Collection Rotation (Alias Swap)
+
+Use when: you need per-period collection configuration (e.g., different quantization or storage settings). [Collection aliases](https://search.qdrant.tech/md/documentation/manage-data/collections/?s=collection-aliases)
+
+1. Create one collection per time period, point a write alias at the newest
+2. Query across all active collections in parallel, merge results client-side
+3. When a new period starts, create the new collection and swap the write alias [Switch collection](https://search.qdrant.tech/md/documentation/manage-data/collections/?s=switch-collection)
+4. Drop the oldest collection outside the window
+
+Trade-off vs shard rotation: allows per-collection config differences, but requires application-level fan-out and more operational overhead.
+
+
+## Filter-and-Delete
+
+Use when: data arrives continuously without clear time boundaries, or you want the simplest setup.
+
+1. Store a `timestamp` payload on every point, create a payload index on it [Payload index](https://search.qdrant.tech/md/documentation/manage-data/indexing/?s=payload-index)
+2. Filter to the desired window at query time using `range` condition [Range filter](https://search.qdrant.tech/md/documentation/search/filtering/?s=range)
+3. Periodically delete expired points using delete-by-filter [Delete points](https://search.qdrant.tech/md/documentation/manage-data/points/?s=delete-points)
+
+- Run cleanup during off-peak hours in batches (10k-50k points) to avoid optimizer locks
+- Deletes are not free: tombstoned points degrade search until optimizer compacts segments
+- Does not reclaim disk instantly (compaction is asynchronous)
+
+
+## Hot/Cold Tiers
+
+Use when: recent data needs fast in-RAM search, older data should remain searchable at lower performance.
+
+- **Shard rotation:** place current shard key on fast-storage nodes, move older shard keys to cheaper nodes via shard placement. All queries still go through a single collection.
+- **Collection rotation:** keep current collection in RAM (`always_ram: true`), move older collections to mmap/on-disk vectors. [Quantization](https://search.qdrant.tech/md/documentation/manage-data/quantization/)
+
+
+## What NOT to Do
+
+- Do not use filter-and-delete for high-volume time-series with millions of daily deletes (use rotation instead)
+- Do not forget to index the timestamp field (range filters without an index cause full scans)
+- Do not use collection rotation when shard rotation would suffice (unnecessary fan-out complexity)
+- Do not drop a shard key or collection before verifying its period is fully outside the retention window
+- Do not skip pre-creating the next period's shard key or collection (write failures during rotation are hard to recover)