Service limits in Azure Search

Maximum limits on storage, workloads, and quantities of indexes, documents, and other objects depend on whether you provision Azure Search at Free, Basic, or Standard pricing tiers.

  • Free is a multi-tenant shared service that comes with your Azure subscription.

  • Basic provides dedicated computing resources for production workloads at a smaller scale.

  • Standard runs on dedicated machines with more storage and processing capacity at every level. Standard comes in four levels: S1, S2, S3, and S3 HD.

    S3 High Density (S3 HD) is engineered for specific workloads: multi-tenancy and large quantities of small indexes (one million documents per index, three thousand indexes per service). This tier does not provide the indexer feature. On S3 HD, data ingestion must leverage the push approach, using API calls to push data from source to index.

Note

A service is provisioned at a specific tier. Jumping tiers to gain capacity involves provisioning a new service (there is no in-place upgrade). For more information, see Choose a SKU or tier. To learn more about adjusting capacity within a service you've already provisioned, see Scale resource levels for query and indexing workloads.

Subscription limits

You can create multiple services within a subscription, each one provisioned at a specific tier, limited only by the number of services allowed at each tier. For example, you could create up to 12 services at the Basic tier and another 12 services at the S1 tier within the same subscription. For more information about tiers, see Choose a SKU or tier for Azure Search.

Maximum service limits can be raised upon request. Contact Azure Support if you need more services within the same subscription.

Resource Free 1 Basic S1 S2 S3 S3 HD
Maximum services 1 12 12 6 6 6
Maximum scale in SU 2 N/A 3 SU 36 SU 36 SU 36 SU 36 SU

1 Free is based on shared, not dedicated, resources. Scale-up is not supported on shared resources.

2 Search units (SU) are billing units, allocated as either a replica or a partition. You need both resources for storage, indexing, and query operations. To learn more about SU computations, see Scale resource levels for query and index workloads.

Storage limits

Storage is constrained by disk space or by a hard limit on the maximum number of indexes, document, or other high-level resources, whichever comes first. The following table documents storage limits. For maximum limits on indexes, documents, and other objects, see limits by resource.

Resource Free Basic 1 S1 S2 S3 S3 HD 2
Service Level Agreement (SLA) 3 No Yes Yes Yes Yes Yes
Storage per partition 50 MB 2 GB 25 GB 100 GB 200 GB 200 GB
Partitions per service N/A 1 12 12 12 3
Partition size N/A 2 GB 25 GB 100 GB 200 GB 200 GB
Replicas N/A 3 12 12 12 12

1 Basic has one fixed partition. At this tier, additional SUs are used for allocating more replicas for increased query workloads.

2 S3 HD has a hard limit of 3 partitions, which is lower than the partition limit for S3. The lower partition limit is imposed because the index count for S3 HD is substantially higher. Given that service limits exist for both computing resources (storage and processing) and content (indexes and documents), the content limit is reached first.

3 Service level agreements (SLAs) are offered for billable services on dedicated resources. Free services and preview features have no SLA. For billable services, SLAs take effect when you provision sufficient redundancy for your service. Two or more replicas are required for query (read) SLA. Three or more replicas are required for query and indexing (read-write) SLA. The number of partitions is not an SLA consideration.

Index limits

Resource Free Basic 1 S1 S2 S3 S3 HD
Maximum indexes 3 5 or 15 50 200 200 1000 per partition or 3000 per service
Maximum fields per index 1000 100 1000 1000 1000 1000
Maximum suggesters per index 1 1 1 1 1 1
Maximum scoring profiles per index 100 100 100 100 100 100
Maximum functions per profile 8 8 8 8 8 8

1 Basic services created after late 2017 have an increased limit of 15 indexes, data sources, and indexers. Services created earlier have 5. Basic tier is the only SKU with a lower limit of 100 fields per index.

Document limits

In most regions, Azure Search pricing tiers (Basic, S1, S2, S3, S3 HD) have unlimited document counts for all services created after November/December 2017. This section identifies the regions where limits apply, and how to determine whether your service is affected.

To determine whether your service has document limits, check the Usage tile in the overview page of your service. Document counts are either unlimited, or subject to a limit based on tier.

Usage tile

Regions and services having document limits

Services having limits were either created before late 2017, or are running on data centers using lower-capacity clusters for hosting Azure Search services. Affected data centers are in the following regions:

  • Australia East
  • East Asia
  • Central India
  • Japan West
  • West Central US

For services subject to document limits, the following maximum limits apply:

Free Basic S1 S2 S3 S3 HD
10,000 1 million 15 million per partition or 180 million per service 60 million per partition or 720 million per service 120 million per partition or 1.4 billion per service 1 million per index or 200 million per partition

Note

For S3 High Density services created after late 2017, the 200 million document per partition has been removed but the 1 million document per index limit remains.

Document size limits per API call

The maximum document size when calling an Index API is approximately 16 megabytes.

Document size is actually a limit on the size of the Index API request body. Since you can pass a batch of multiple documents to the Index API at once, the size limit realistically depends on how many documents are in the batch. For a batch with a single document, the maximum document size is 16 MB of JSON.

To keep document size down, remember to exclude non-queryable data from the request. Images and other binary data are not directly queryable and shouldn't be stored in the index. To integrate non-queryable data into search results, define a non-searchable field that stores a URL reference to the resource.

Indexer limits

Basic services created after late 2017 have an increased limit of 15 indexes, data sources, skillsets, and indexers.

Resource-intensive operations, such as image analysis in Azure blob indexing or natural language processing in cognitive search, have shorter maximum running times so that other indexing jobs can be accommodated. If an indexing job cannot complete within the maximum time allowed, try running it on a schedule. The scheduler keeps track of indexing status. If a scheduled indexing job is interrupted for any reason, the indexer can pick up where it last left off at the next scheduled run.

Resource Free 1 Basic 2 S1 S2 S3 S3 HD 3
Maximum indexers 3 5 or 15 50 200 200 N/A
Maximum datasources 3 5 or 15 50 200 200 N/A
Maximum skillsets 4 3 5 or 15 50 200 200 N/A
Maximum indexing load per invocation 10,000 documents Limited only by maximum documents Limited only by maximum documents Limited only by maximum documents Limited only by maximum documents N/A
Maximum running time 5 1-3 minutes 24 hours 24 hours 24 hours 24 hours N/A
Maximum running time for cognitive search skillsets or blob indexing with image analysis 5 3-10 minutes 2 hours 2 hours 2 hours 2 hours N/A
Blob indexer: maximum blob size, MB 16 16 128 256 256 N/A
Blob indexer: maximum characters of content extracted from a blob 32,000 64,000 4 million 4 million 4 million N/A

1 Free services have indexer maximum execution time of 3 minutes for blob sources and 1 minute for all other data sources.

2 Basic services created after late 2017 have an increased limit of 15 indexes, data sources, and indexers. Services created earlier have 5.

3 S3 HD services do not include indexer support.

4 Maximum of 30 skills per skillset.

5 Cognitive search workloads and image analysis in Azure blob indexing have shorter running times than regular text indexing. Image analysis and natural language processing are computationally intensive and consume disproportionate amounts of available processing power. Running time was reduced to give other jobs in the queue an opportunity to run.

Queries per second (QPS)

QPS estimates must be developed independently by every customer. Index size and complexity, query size and complexity, and the amount of traffic are primary determinants of QPS. There is no way to offer meaningful estimates when such factors are unknown.

Estimates are more predictable when calculated on services running on dedicated resources (Basic and Standard tiers). You can estimate QPS more closely because you have control over more of the parameters. For guidance on how to approach estimation, see Azure Search performance and optimization.

API Request limits

  • Maximum of 16 MB per request 1
  • Maximum 8 KB URL length
  • Maximum 1000 documents per batch of index uploads, merges, or deletes
  • Maximum 32 fields in $orderby clause
  • Maximum search term size is 32,766 bytes (32 KB minus 2 bytes) of UTF-8 encoded text

1 In Azure Search, the body of a request is subject to an upper limit of 16 MB, imposing a practical limit on the contents of individual fields or collections that are not otherwise constrained by theoretical limits (see Supported data types for more information about field composition and restrictions).

API Response limits

  • Maximum 1000 documents returned per page of search results
  • Maximum 100 suggestions returned per Suggest API request

API Key limits

Api-keys are used for service authentication. There are two types. Admin keys are specified in the request header and grant full read-write access to the service. Query keys are read-only, specified on the URL, and typically distributed to client applications.

  • Maximum of 2 admin keys per service
  • Maximum of 50 query keys per service