How to Debug Qdrant with Metrics

First check optimizer status. Most production issues trace back to active optimizations competing for resources. If optimizer is clean, check memory, then request metrics.

Optimizer Stuck or Too Slow

Use when: optimizer running for hours, not finishing, or showing errors.

• Use

  /collections/{collection_name}/optimizations

  endpoint (v1.17+) to check status Optimization monitoring
• Query with optional detail flags:

  ?with=queued,completed,idle_segments

• Returns: queued optimizations count, active optimizer type, involved segments, progress tracking
• Web UI has an Optimizations tab with timeline view and per-task duration metrics Web UI
• If

  optimizer_status

  shows an error in collection info, check logs for disk full or corrupted segments
• Large merges and HNSW rebuilds legitimately take hours on big datasets. Check progress before assuming it's stuck.

Memory Seems Too High

Use when: memory exceeds expectations, node crashes with OOM, or memory keeps growing.

• Process memory metrics available via

  /metrics

  (RSS, allocated bytes, page faults)
• Qdrant uses two types of RAM: resident memory (data structures, quantized vectors) and OS page cache (cached disk reads). Page cache filling available RAM is normal. Memory article
• If resident memory (RSSAnon) exceeds 80% of total RAM, investigate
• Check

  /telemetry

  for per-collection breakdown of point counts and vector configurations
• Estimate expected memory:

  num_vectors * dimensions * 4 bytes * 1.5

  for vectors, plus payload and index overhead Capacity planning
• Common causes of unexpected growth: quantized vectors with

  always_ram=true

  , too many payload indexes, large

  max_segment_size

  during optimization

Queries Are Slow

Use when: queries slower than expected and you need to identify the cause.

• Track

  rest_responses_avg_duration_seconds

  and

  rest_responses_max_duration_seconds

  per endpoint
• Use histogram metric

  rest_responses_duration_seconds

  (v1.8+) for percentile analysis in Grafana
• Equivalent gRPC metrics with

  grpc_responses_

  prefix
• Check optimizer status first. Active optimizations compete for CPU and I/O, degrading search latency.
• Check segment count via collection info. Too many unmerged segments after bulk upload causes slower search.
• Compare filtered vs unfiltered query times. Large gap means missing payload index. Payload index

What NOT to Do

• Ignore optimizer status when debugging slow queries (most common root cause)
• Assume memory leak when page cache fills RAM (normal OS behavior)
• Make config changes while optimizer is running (causes cascading re-optimizations)
• Blame Qdrant before checking if bulk upload just finished (unmerged segments)