# Flow on Helios Sizing Guidelines

## Overview

Sizing guidelines help users make decisions on selecting the right Flow instance size on SingleStore Helios for their migration or data movement jobs.

## Size a Workload

When selecting a Flow instance, evaluate your workload carefully. Consider the following  key parameters:

1. **Data Size**

   * The total volume of data that needs to be migrated or streamed.
   * Includes both historical data and incremental changes.
   * Larger datasets generally require larger Flow instances to achieve migration in a reasonable timeframe.

2. **Number of Tables**

   * The count of tables involved in the job/pipeline.
   * A higher number of tables increases concurrency requirements and can benefit from larger Flow instances.

3. **Size of the Biggest Table**

   * The largest table in your workload may become a bottleneck.
   * If the largest table is very large (hundreds of GBs or TBs), it may dictate the minimum Flow size you need.

4. **Number of Threads on Source Database**

   * Determines the maximum parallelism you can achieve when reading from the source.
   * If your source can’t provide enough threads, increasing Flow instance size may not help.

5. **Estimated Time to Complete the Job**

   * The timeframe in which you want the migration to finish (e.g., overnight, within a maintenance window, or real-time).
   * Tighter SLAs require more compute and memory resources.

## Sizing Examples

| Workload Type                     | Data Size                     | Number of Tables | Biggest Table Size       | Threads Available | Completion Time Target   | SuggestedFlowInstance |
| --------------------------------- | ----------------------------- | ---------------- | ------------------------ | ----------------- | ------------------------ | --------------------- |
| Small                             | \~50 GB                       | 10               | \~8 GB                   | 4                 | 12 - 24 hours            | f - 1                 |
| Medium                            | \~500 GB                      | 50 - 75          | \~100 GB                 | 8 - 12            | 6 - 8 hours              | f - 3                 |
| Large                             | \~2 TB                        | 200+             | \~400 GB                 | 16                | \~6 hours                | f - 6                 |
| Very Large/Enterprise             | \~10 TB                       | 500+             | \~1 TB                   | 32+               | < 4 hours (tight SLA)    | f - 8                 |
| Latency Sensitive/ Real-time Sync | \~300 GB/day (ongoing stream) | 20 - 30          | \~200 GB (growing daily) | 12 - 16           | Continuous / < 1 min lag | f - 4                 |

**Additional Notes**

* **Thread Utilization on Source Database Server**

  Increasing the number of threads used on the source database server proportionally increases the load on system resources (CPU, memory, I/O). Proper sizing and monitoring are recommended to prevent performance degradation.
* **Completion Time Target**

  The Completion Time Target represents an estimated duration derived from internal performance testing. Actual completion times may vary depending on the source database server's ability to transmit records at the required rate.
* **Data Flow Behavior**

  During the initial data load, the system performs a bulk load operation in a sequential manner to ensure data consistency and reliability.
* **Handling Large Tables**

  For very large tables, SingleStore recommends using  XL Ingest to optimize throughput and reduce load time.

***

Modified at: September 29, 2025

Source: [/db/v9.1/load-data/load-data-with-singlestore-flow-on-helios/flow-on-helios-sizing-guidelines/](https://docs.singlestore.com/db/v9.1/load-data/load-data-with-singlestore-flow-on-helios/flow-on-helios-sizing-guidelines/)

(An index of the documentation is available at /llms.txt)