Size and test a dedicated read nodes index

Calculate the size of your index

To determine how many shards your index requires, calculate your index size and then apply the number of shards formula.

Index size

A record can include a dense vector, a sparse vector, or both. Use the formula that matches your data to calculate total size:

Index of dense vectors
Index of sparse vectors
Index with both dense and sparse vectors

An index of dense vectors contains records with one dense vector each.

Records can also contain sparse vectors (when the index metric is set to dotproduct), which can be useful for hybrid search. To learn how to calculate size in that case, see Index with both dense and sparse vectors.

Calculate size (assuming no sparse vectors)

Index size = Number of records × (
               ID size + 
               Metadata size +
               Dense vector dimensions × 4 bytes
             )

Where:

ID size and Metadata size are measured in bytes, averaged across all records.
Each Dense vector dimension uses 4 bytes.

Example calculationsThese examples assume 8-byte IDs:

Records	Dense vector dimensions	Avg metadata size	Index size
500,000	768	500 bytes	1.79 GB
1,000,000	1536	1,000 bytes	7.15 GB
5,000,000	1024	15,000 bytes	95.5 GB
10,000,000	1536	1,000 bytes	71.5 GB

Example: 500,000 records × (8-byte ID + (768 dense vector dimensions × 4 bytes) + 500 bytes of metadata) = 1.79 GB

An index of sparse vectors contains records with one sparse vector each.Calculate size

Index size = Number of records × (
               ID size + 
               Metadata size +
               Number of non-zero sparse values × 8 bytes
             )

Where:

ID size and Metadata size are measured in bytes, averaged across all records.
Number of non-zero sparse values: Average number across all records. To find the count for a single record, check the length of the sparse vector’s indices or values array. Each non-zero value uses 8 bytes.

Example calculationsThese examples assume 8-byte IDs:

Records	Avg number of non-zero sparse values	Avg metadata size	Index size
500,000	10	500 bytes	0.29 GB
1,000,000	50	1,000 bytes	1.41 GB
5,000,000	100	15,000 bytes	79.0 GB
10,000,000	50	1,000 bytes	14.1 GB

Example: 500,000 records × (8-byte ID + (10 non-zero sparse values × 8 bytes) + 500 bytes of metadata) = 0.29 GB

An index with both dense and sparse vectors contains records that each have one dense vector and an optional sparse vector.Calculate size

Index size = Number of records × (
               ID size + 
               Metadata size +
               Dense vector dimensions × 4 bytes + 
               Number of non-zero sparse values × 8 bytes
             )

Where:

ID size and Metadata size are measured in bytes, averaged across all records.
Each Dense vector dimension uses 4 bytes.
Number of non-zero sparse values: Average number across all records, including those without sparse vectors. To find the count for a single record, check the length of the sparse vector’s indices or values array. Each non-zero value uses 8 bytes.

Example calculationsThese examples assume 8-byte IDs:

Records	Dense vector dimensions	Avg number of non-zero sparse values	Avg metadata size	Index size
500,000	768	10	500 bytes	1.83 GB
1,000,000	1536	50	1,000 bytes	7.54 GB
5,000,000	1024	100	15,000 bytes	99.5 GB
10,000,000	1536	50	1,000 bytes	75.4 GB

Example: 500,000 records × (8-byte ID + (768 dense vector dimensions × 4 bytes) + (10 non-zero sparse values × 8 bytes) + 500 bytes of metadata) = 1.83 GB

Number of shards

To calculate the number of shards your index requires, divide the size of your index by 250 GB and round up:

Minimum shards = (Index size) / (250 GB per shard)

To maintain optimal performance, provision additional shards to keep your index at 70-80% capacity. For example, a 500 GB index should have three shards (750 GB capacity = 67% full), not two shards (500 GB capacity = 100% full).

Example shard calculations

Index size	Minimum shards	Recommended shards
~71 GB	1 (250 GB; 28% full)	1 (250 GB; 28% full)
~300 GB	2 (500 GB; 60% full)	2 (500 GB; 60% full)
~400 GB	2 (500 GB; 80% full)	3 (750 GB; 53% full)

Other considerations

Every index must have at least one shard. However, you can pause an index by reducing its replicas to 0.
After you’ve created your index, monitor its fullness.

Add shards when index fullness reaches 70-80%, especially if you expect continued growth. Adding shards reduces storage fullness (index data is spread across shards, so each stores less) and memory fullness (with less data per shard, there’s less to cache in memory), helping you avoid write failures.

Number of replicas

To calculate the number of replicas your index requires, first test your workload to find the QPS a single replica can handle at your target latency. Then, use this formula, and round up:

Minimum replicas = (Required QPS) / (QPS per replica)

For example, if one replica handles 50 QPS at your target latency and you need 150 QPS, you need three replicas. For how throughput scales with replicas and how to size for high availability, see Replicas.

Test your workload

To choose between on-demand and dedicated read nodes, or to optimize your dedicated read nodes configuration, test with your actual workload. Performance varies based on factors such as the size of your index, vector dimensionality, metadata characteristics, and query patterns.

Calculate the size of your index

Determine how many shards your index requires. See Calculate the size of your index.

Create and populate a test index

Populate a dedicated read nodes index with data representative of your workload.

If you don’t restore your test index from a backup, you can upsert or import your data.

Migrate your test index to dedicated read nodes (if necessary)

If your test index is on-demand, migrate it with a single b1 replica to start.

Don’t migrate your production index yet. At this point, you’re just testing your workload.

Run a load test

Send realistic query patterns against your test index, gradually increasing QPS. For example, start at 10 QPS for about 30 minutes, then step up in 10-QPS increments while monitoring latency. Note the QPS where latency crosses your target threshold.

Calculate replicas

From the QPS a single replica sustained, determine how many replicas you need for your target throughput.

Adjust and re-test

If you haven’t hit your performance and cost goals, change the configuration and test again:

Add or remove shards for storage capacity
Add or remove replicas for throughput
Change node types for different performance characteristics

Continue iterating until you meet your requirements with room for growth.

Get started

Core concepts

Index data

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Operations

Using pods

Size and test a dedicated read nodes index

Calculate the size of your index

Index size

Number of shards

Example shard calculations

Other considerations

Number of replicas

Test your workload

​Calculate the size of your index

​Index size

​Number of shards

​Example shard calculations

​Other considerations

​Number of replicas

​Test your workload

Calculate the size of your index

Index size

Number of shards

Example shard calculations

Other considerations

Number of replicas

Test your workload