Efficient satellite imagery supply with AWS Serverless at BASF Digital Farming GmbH

This post was co-written with Dr. Jan Melchior at BASF Digital Farming GmbH and xarvio Digital Farming Solutions.

BASF Digital Farming’s mission is to support farmers worldwide with cutting-edge digital agronomic decision advice by using its main crop optimization platform, xarvio FIELD MANAGER. This necessitates providing the most recent satellite imagery available as quickly as possible. This blog post describes the serverless architecture developed by BASF Digital Farming for efficiently downloading and supplying satellite imagery from various providers to support its xarvio platform.

Figure 1. Screenshot showing the xarvio Field Manager platform

Architecture

Figure 2 shows the serverless architecture implemented with AWS services for downloading and processing satellite imagery. The subscription management components handle subscription creation, updates, and deletions, while the actual data downloading and processing occurs in AWS Step Functions.

Figure 2. Serverless implementation of the new imagery service

1. Subscriptions are created using Amazon API Gateway for external API access, which provides request throttling and can be used to manage API request authorizations.
2. An AWS Lambda API function manages subscriptions. It implements common create, read, update, and delete operations with request validations and provides an endpoint for replaying failed requests. Subscriptions contain geometry, data provider, as well as start and end date and other parameters, which are stored in the subscription database (Step 7) before a message is sent out for processing.
   Notice that the entire architecture is serverless and thus allows for theoretically unbounded scaling. In case of a bug, this can lead to severe cost impacts, so we implemented a safety buffer, which enables us to prioritize and limit the number of Step Functions executions of the processing pipeline.
3. All requests (such as the initial request for imagery when a subscription is created) are sent to the Amazon Simple Queue Service (Amazon SQS) processing queue first, which functions as a processing buffer and allows for request prioritization.
4. Subsequently, Amazon EventBridge Pipes connects the processing buffer with AWS Step Functions. It handles pipe-internal errors automatically; for example, when the Step Functions concurrency limit is reached, the invocation will be retired automatically. This does not handle exceptions raised within Step Functions, such as runtime errors.
5. AWS Step Functions then performs the actual downloading, processing, and ingestion to the STAC catalog of satellite data from different providers. In case of failure, the request message with error description is sent to the failure queue.
6. Step Functions uploads the data to Amazon Simple Storage Service (Amazon S3), which stores satellite imagery data.
7. Following this, Step Functions updates the subscriptions in the Amazon DynamoDB-based subscription database, which stores relevant metadata, such as start and end date, boundary, provider, collection, and last update.
8. A notification is sent out to inform the user that new data is available through Amazon Simple Notification Service (Amazon SNS), which informs users and services about any updates on a subscription, such as new data being available or subscriptions having been created, deleted, updated, or having failed.
9. Next, the data is published to our internal STAC catalog, which registers the satellite imagery and makes it directly accessible for subsequent processing.
10. In case of failed Step Functions execution in Step 5, the Amazon SQS-based failure queue buffers failed executions. Failure messages contain the error message and request body. Depending on error reasons, they can be replayed using the corresponding API endpoint, enabling reprocessing through the replay endpoint on the API Lambda function. The endpoint also allows users to filter messages based on their failure type and to delete messages that cannot be replayed.
11. An update checker, built on AWS Lambda, regularly checks whether a subscription can be updated. It is triggered in conjunction with an event scheduler every 5 minutes, checks the database for subscriptions that can be updated, and sends update request messages to the processing buffer. Besides actively checking resources, such as API endpoints and STAC catalogs, it also sends out an update message if a notification was received, for example, through an external notification service.
12. Finally, a delete checker, also built on AWS Lambda, identifies subscriptions that can be deleted. It is triggered in conjunction with an event scheduler every 12 hours. It regularly checks the database for subscriptions that can be deleted and removes them from the database, the S3 bucket, and the STAC catalog. As a safety mechanism, a subscription will first be marked for deletion for 6 months before it gets deleted.

Imagery step function

The actual downloading and processing of data from different providers is handled by the imagery function, illustrated for two different providers (Public and Planet) in Figure 3.

Figure 3. Diagram showing detail state machine for the Imagery Step Function

1. When a request arrives, the provider choice state determines the provider from the request body, depending on which the Step Functions flow routes to different Lambda states.
2. In case a public provider is selected (for example, Earth Search), the Public_Provider Lambda function downloads the data from STAC-based open data providers and directly uploads it to the S3 data bucket, as shown in Figure 2.
3. In case Planet data is selected, the data retrieval involves an asynchronous call to an external API: First, the Planet_Requester sends an order to the Planet API, together with a task token for pausing Step Functions and the URL of the Planet_Webhook Lambda function.
4. The Planet_Webhook function is invoked by Planet when the requested order is available for downloading. Given the transmitted task token, Step Functions is resumed with the next state.
5. Subsequently, the Planet_Provider Lambda function downloads and processes the Planet data.
6. For both public providers and Planet, the subsequent Public_Provider Lambda function updates the subscription database entries, as shown in Figure 2 (for example, with the latest available timestamp), and adds the download and processed data to the internal STAC catalog, before it ends in the Success state.
7. If an error occurs in any of the Lambda functions (2, 3, 5, 6), an error message is prepared in the Error_Parsing If an unknown provider is handed in, an error message, including the request body, is prepared in the Error_Provider_Unknown state. In both cases, the error message is pushed to the Failure_Queue (refer to #10 of Figure 2), before it ends in the Failure state.

Conclusion

BASF Digital Farming GmbH developed a serverless architecture on AWS for efficiently downloading and supplying satellite imagery for use by its xarvio platform. This architecture led to a 5x faster delivery rate, an 80% cost reduction through on-demand data downloading, and a 3x accelerated development cycle. Future work will include optimizing the architecture, exploring additional AWS services, and onboarding more satellite imagery providers. Similar serverless architectures using AWS services like AWS Step Functions, AWS Lambda, and Amazon API Gateway can enhance flexibility, scalability, and cost efficiency in imagery provisioning. Learn more about AWS serverless offerings at thinkwithwp.com/serverless.