Data

Ampt provides a fast, flexible, and scalable NoSQL datastore that's integrated into every Ampt Environment. Backed by Amazon DynamoDB, the @ampt/data interface lets developers manage massive collections of complex objects that can be queried on multiple dimensions, sorted, and paginated. With single-digit millisecond response times, it provides enough power to cover your most common needs and use cases.

Your data is just there as part of your application's runtime. You don't need to think about connection strings, credentials, capacity planning, or database maintenance. You can get, set, and remove data whenever you need access to state.

Plus, Ampt provides isolated databases to each AMPT ENVIRONMENT, enabling developers to have independent copies of application data in each sandbox, preview, and stage of every app.

Getting started #

To access data from your application, you must install the @ampt/data npm package. You can install this using the npm command line tool:

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npm install @ampt/data

Or via the Ampt shell:

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ampt  ›︎ install @ampt/data ▊

The data interface makes API calls in order to interact with the underlying database, so any handlers or functions that use data must use async/await.

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import { data } from "@ampt/data";
import { api } from "@ampt/api";

api("my-api")
  .router("/test-data")
  .get("/", async (event) => {
    // Set and get data
    await data.set("foo", "bar");
    const results = await data.get("foo");
  });

Understanding data structures #

The data interface provides a simple, but extremely powerful abstraction over a NoSQL database that is automatically provisioned, configured, and managed for you. All you need to do is set and get data using a key. Items can be stored as a single value (string, boolean, number, array, etc.) or as a complex object with nested values.

Storing single values #

For simple key-value use cases, items can store a single attribute value:

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await data.set("foo", "bar"); // string
await data.set("foo", 123); // number
await data.set("foo", true); // boolean
await data.set("foo", ["arr1", "arr2"]); // array

When updating a single value, the entire "value" is overwritten.

Storing objects #

For more complex data structures, items can store JavaScript objects:

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await data.set("foo", {
  var1: "some string value",
  var2: 123,
  var3: false,
  var4: ["arr1", "arr2"],
  var5: { var6: "nested object" },
});

Object root keys can be added, updated, and removed independently of one another, allowing for partial updates:

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await data.set("foo", {
  var1: "this value will be updated",
  var3: null, // or 'undefined' will be removed
  var7: "this value will be added",
});

The operation above will update the item to this:

{
  "var1": "this value will be updated",
  "var2": 123,
  "var4": ["arr1", "arr2"],
  "var5": { "var6": "nested object" },
  "var7": "this value will be added"
}

Meta data #

In addition to the key and value attributes, meta data is used to provide additional information about an item.

Every item has a created and modified date (both returned as ISO 8601 format in UTC). When setting items, the created date will be added if the item doesn't exist. The modified date will be updated every time the item is set. If overwriting an item, you can maintain the created date using a Created timestamp integrity check.

User-defined meta data includes a ttl (see Setting items) and Labels.

Collections #

Collections let you group items together and then retrieve them using more advanced query options. You can think of collections like folders in a file system that keep items organized. Collections are defined by adding a "namespace" and a colon (:) before the item's key. For example, if you wanted to save a user record for jane@doe.com in the "users" collection, you would set the key to users:jane@doe.com like this:

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await data.set("users:jane@doe.com", {
  name: "Jane Doe",
  email: "jane@doe.com",
  title: "Senior Developer",
});

To retrieve this single item, you would provide the entire key (including the collection namespace) like this:

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await data.get("users:jane@doe.com");

Storing items in collections opens up a number of powerful use cases. You can query with conditionals, allowing you to retrieve select items from a collection, and you can sort on keys in lexicographical order, which is great for dates or KSUIDs.

Labels #

Key-value stores typically work by using a single key to reference stored items. This is fine when you know the item's key (such as an email address or userId) and only need to access it using that value. However, our applications often need to use multiple access patterns in order to retrieve data. This is where Labels help you add additional context and retrieval capabilities.

Labels use the same format as item keys and support collections as well. For example, if we stored a product using a simple key like productId-12345, we could add a label like this:

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await data.set(
  "productId-12345",
  {
    // my product data here
  },
  { label1: `product-released:2023-07-01` }
);

Now we can either retrieve the item by its key using:

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await data.get("productId-12345");

Or by its label:

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await data.getByLabel("label1", "product-released:2023-07-01");

Unlike keys, labels DO NOT NEED TO BE UNIQUE. This means that multiple items can share the same exact label value, giving you the ability to return a group of items (as in the example above) that have the same "released" date. Like keys, labels can be queried with conditionals if using a collection.

Labels also support default values. This allows you to only overwrite a label's value if it isn't already set on an item. To set a default value for a label, wrap the value in a single item array:

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await data.set("myKey", "myValue", {
  label1: "someLabel", // overwrite label1
  label2: ["defaultLabel"], // overwrite if label2 doesn't exist
});

If you wish to remove a label, you can set its value to null or undefined:

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await data.set("myKey", "myValue", {
  label1: undefined, // remove this label
});

Setting items #

Setting a data item can be accomplished using the set method. You provide a key as the first argument and a value (either a string, boolean, number, array, or object) as the second parameter. Keys are case sensitive, can be a string of up to 256 bytes each, and can contain any valid utf-8 character including spaces. By default, the set command will return the updated item.

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await data.set("foo", "bar");
await data.set("fooNum", 123456);
await data.set("foo-Bool", true);
await data.set("foo_Array", ["val1", "val2", "val3"]);
await data.set("foo Obj", { key1: "some val", key2: "some other val" });

An options object can be passed as third argument. The following options are supported:

Setting data with an options object:

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await data.set("foo", "bar", {
  meta: true,
  overwrite: true,
  ttl: 3600,
  label1: "baz",
  label2: "baz:bat",
});

Setting multiple items #

To set multiple items at the same time, you can specify an array of objects that each contain a key and value as well as any additional meta data (e.g. labels and a ttl value) and default values as the first argument of the set method. You can specify up to 25 items in each request. The second parameter must be an options object with the overwrite flag set to true. This is for future compatibility to support batch updates. You can also add a meta: true flag to return the metadata of your items.

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const results = await data.set(
  [
    { key: "key1", value: "string value" },
    { key: "someOtherKey", value: 123, ttl: 1000, label1: "foo:baz" },
    {
      key: "namespacedKey:keyX",
      value: { foo: "bar" },
      default: { bat: "baz" },
    },
  ],
  { overwrite: true }
);

Existence checks #

Using the exists flag, you can enable a conditional check before adding or updating an item. If no exists flag is provided, set operations on single items (without the overwrite: true flag) will default to UPSERTS, creating the item if it doesn't exist, or updating it if it does.

To add an item ONLY if it DOES NOT EXIST, set the exists flag to false. Single item set operations (with or without the overwrite:true) will fail with an Item already exists error.

To update an item ONLY if it DOES EXIST, set the exists flag to true. Single item set operations (with or without the overwrite:true) will fail with an Item does not exist error.

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// This will fail if "myKey" already exists
await data.set("myKey", "someValue", { exists: false });

// This will fail if "myKey" doesn't exists
await data.set("myKey", { foo: "bar" }, { exists: true });

Setting default values #

Defaults let you conditionally update an item's value if one doesn't already exist. You can provide a default for an item that stores a single value, but they are most useful when working with objects.

For example, the set operation below would overwrite key1 with "myValue" whether it existed or not, but key2 would only be written if the attribute didn't exist.

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await data.set(
  "myKey",
  { key1: "myValue" },
  {
    default: { key2: "defaultVal2" },
  }
);

When using objects, defaults are merged (using a deep merge) with the provided value. This allows you to provide default values for fields without worrying about the input data. For example:

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const input = req.body;

await data.set("myKey", input, {
  default: { key1: "defaultVal1", key2: "defaultVal2", key3: "defaultVal3" },
});

If input specified a value for key2, then that value would be saved instead of the default value.

A default value can be used with single value items by setting the value of the item to undefined or null.

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await data.set("myKey", undefined, { default: "defaultValue" });

This is useful if you only want to set a value if it doesn't already exist. If the value already exists, the operation will succeed and the item's modified date will be updated. If you want to prevent the item from being updated at all, you can use existence checks.

Using atomic counters #

Atomic counters allow numeric items or numeric item object values to be atomically updated. Atomic updates ensure that addition and subtraction operations are processed in order, giving users the ability to maintain the integrity of counters even if there are multiple simultaneous requests.

Updating a single value atomically #

If you only need to update a single value, Ampt provides the add method to help you do that. If the item is a simple numeric value (e.g. { key: "myCounter", value: 10 }, you provide the full key name (including collection namespace) as the first parameter and the numeric value you want to "add" to the existing value as the second parameter. Numbers can be positive or negative and atomic counters support both integers and float values.

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const results = await data.add("myCounter", 1);
const results = await data.add("myNegativeCounter", -1);

The add method will return the updated value by default. You can specify an optional third parameter of true to return the item's metadata, or pass in an options object like { meta: true }.

If the value you want to atomically update is nested within an object, you specify the full key name as the first parameter, the name of the nested object key you want to update as the second parameter, and a numeric value as the third parameter.

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const results = await data.add("myObjectKey", "nestedCounter", 5);

The add method will return the updated object by default. You can specify an optional fourth parameter of true to return the item's metadata, or pass in an options object like { meta: true }.

Updating multiple values atomically #

You may want to atomically update several fields with a single item and potentially update other values as well. You can achieve this using the standard set method along with a special $add keyword. You set an item like you normally would, but for any numeric value that you'd like to atomically update, you specify a value of { $add: 1 }, where 1 is whatever value you wish to add. For example:

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const results = await data.set("myObject", {
  nestedCounter: { $add: 1 },
  anotherCounter: { $add: 5 },
  someOtherValue: "foo",
});

In the example above, nestedCounter will be atomically increased by 1 on every call and anotherCounter will be atomically increased by 5.

Getting items #

Items can be retrieved using the get method. This method takes the key as the first argument, and an optional options object as the second argument. By default, the get method will return the value stored in the item.

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const result = await data.get("foo");

In addition to retrieving a single key, you can also retrieve items by providing the collection namespace followed by a colon and a * as a wildcard.

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const result = await data.get("my-namespace:*");

This will return an items array with all keys in the namespaced collection. By default, the items will be limited to 100 and the keys will be sorted in ascending lexicographical order. These defaults can be changed by providing an options object as the second argument.

The following options are supported:

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const users = await data.get("users:*", { limit: 10, reverse: true });

If the only option you need to pass is { meta: true }, you can simply pass true as the second argument to the get method.

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const results = await data.get("foo", true);
const results = await data.get("users:*", true);

Ampt either returns a single item or an array of multiple items. Any get request that specifies an exact key match will return a single item. Any request that could return more than one item will return an object with an items array that contains keys and values:

{
  items: [
    { key: "foo:bar", value: "item1" },
    { key: "foo:bat", value: { some: "value" } },
    { key: "foo:baz", value: 1234 },
  ];
}

Pagination #

The total number of items returned by a single get() call is limited to the value specified by the limit parameter (default 100). If additional items are available, a lastKey will be returned. This value can be passed into a subsequent call to get() as the start parameter. A .next() convenience function will also be returned which can be called directly instead of constructing the additional call.

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const result = await data.get("foo:*", { limit: 3 });

{
	items: [
		{ key: "foobar", value: "item1" },
		{ key: "foobat", value: true" },
		{ key: "foobaz", value: 1234 },
	],
	lastKey: "foobaz",
	next: [Function: next]
}

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const nextResult = await data.get("foo:*", { limit: 3, start: "foobaz" });

To paginate through all items using next():

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const result = await data.get("foo:*", { limit: 3 });

while (result) {
  // do something with result.items
  result = result.next ? await result.next() : null;
}

Querying with conditionals #

Partial matches #

You've already seen the * wildcard used to retrieve all items, but you can also use the wildcard to retrieve items with partially matching keys as well.

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// Retrieve all keys from the `user123` collection
const results = await data.get("user123:*");

// Retrieve all keys from the `user123` collection that start with 'orders'
const results = await data.get("user123:orders*", true);

Greater than and less than #

Keys in collections are sorted in lexicographical order, so you can retrieve all items from a collection that are greater than, greater than or equal to, less than, or less than or equal to a supplied key. Use the standard symbols (>, >=, <, <=) after the collection name and colon to filter the return items.

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// Retrieve all keys from the `user123` collection greater than 2021-05-18
const results = await data.get("user123:>2021-05-18");

// Retrieve all keys from the `user123` collection greater than or equal to 2021-05-18
const results = await data.get("user123:>=2021-05-18");

// Retrieve all keys from the `user123` collection less than 2021-05-18
const results = await data.get("user123:<2021-05-18");

// Retrieve all keys from the `user123` collection less than or equal to 2021-05-18
const results = await data.get("user123:<=2021-05-18");

Retrieving items between two keys #

If you want to retrieve items that are lexicographically between two keys, specify the two partial keys between a |.

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// Retrieve all keys between 2021-05-01 and 2021-05-31
const results = await data.get("user123:2021-05-01|2021-05-31");

Getting items by their labels #

You can get items by their labels using the get method and the { label: 'labeln' } option, or you can use the getByLabel convenience method. This method takes the label as the first parameter (e.g. label3), the key as the second parameter, and then an optional third parameter that accepts all the same options as the get method.

Labels support collections as well as simple keys. Since they behave the same way, you can also use collection querying methods like * and >= on labels as well.

Labels are incredibly powerful, allowing you to pivot and access your data in multiple "views". For example, if you store orders in a "user" collection (e.g. user-1234), then you can store their order date and number as the key (e.g. user-1234:ORDER_2021-05-18_9321). This would let you list all (or some) of their orders and sort them by date. But if you wanted to access this same information by the unique order number (9321), a simple key-value store wouldn't let you. You can set label1 to something like ORDER-9321. Now you can either get the orders BY USER or BY ORDER ID:

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// Set the order
const newOrder = await data.set(
 'user-1234:ORDER_2021-05-18_9321', // the key
 { ...the-order-data-here... }, // the details of the order
 { label1: 'ORDER-9321' } // our order id label
)

// Get all orders for user-1234
const user_orders = await data.get('user-1234:ORDER_*');

// Get ORDER 9321
const order = await data.getByLabel('label1','ORDER-9321');

Getting multiple items by their key #

If you'd like to retrieve multiple items that aren't part of the same collection, you can specify an array of keys as the first argument in the get method. Keys must be the complete key as wildcards and other conditionals are not supported in batch operations. You can specify up to 25 keys in each request.

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const results = await data.get(["key1", "someOtherKey", "namespacedKey:keyX"]);

Removing items #

You can remove items by providing an item's key or an array of keys to the remove() method. Keys must be the complete key as wildcards and other conditionals are not supported in the remove operation. You can specify up to 25 keys in each request.

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const results = await data.remove("foo");
const results = await data.remove("foo:bar");
const results = await data.remove([
  "key1",
  "someOtherKey",
  "namespacedKey:keyX",
]);

Reacting to changes in data #

Ampt runtime emits an event every time a record is created, updated, or deleted, which you can react to by writing an event handler. This lets you decouple your application and process changes to your data asynchronously. For example, your API could set data and then immediately send a response, while your event handler can do some data aggregation or send a request to an outside app.

Defining event handlers #

You define an event handler using the data.on() method.

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data.on("created", async (event) => {
  // an item has been created
});

The first argument is the event name: created, updated, or deleted. The second argument is your handler function, which receives a single "event" argument.

You can also react to more than one event using an array of event names, or * to react to any event:

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data.on(["created", "updated"], async (event) => {
  // an item has been created or updated
});

data.on("*", async (event) => {
  // an item has been created, updated, or deleted
});

It's possible for more than one handler to be called for a given change to a data item, in which case the handlers are called in the order they were defined. In the example above, the first handler will always be called before the second handler when an item is created or updated, and only the second handler will be called when an item is deleted.

Event format #

The event passed to your handler has the following properties:

• name: the event name (either created, updated, or deleted)
• item: the item, including metadata and the value of the item in the value property
• previous: the previous state of the item when the event is updated

Filtering by key #

You can define a handler that is only called when specific keys are affected by adding namespace and key filters to the event name.

To add a filter you can use one of these formats:

• <event-name>:<key-filter>
• <event-name>:<namespace-filter>:<key-filter>

Each filter can either be an exact string or a prefix by adding * to the end of the filter.

For example, to filter using a specific simple key:

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data.on("*:global-item", (event) => {
  // called when the item with key `global-item` is created, updated or deleted
});

To filter using a simple key prefix:

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data.on("created:order_*", (event) => {
  // called when an item with a simple key starting with `order_` is created
});

To filter using both a namespace and key prefix:

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data.on("created:order_*:item_*", (event) => {
  // called when an item is created that has a namespace starting with `order_`
  // and a key starting with `item_`
});

Event ordering #

Data events are processed in the order that the changes were applied to your data items, within an item namespace. It's possible for multiple handlers to be invoked in parallel, but for different namespaces.

Handling errors #

If a handler throws an error, it will be retried with exponential backoff for up to 24 hours until it succeeds. After 24 hours the event will be dropped.

Handlers should only throw an exception for "retryable" errors such as downstream request failures. If the error is a permanent error, the handler should use a try-catch block to capture the error and let the handler succeed.

Avoiding event loops #

It's possible to create an "event loop" where your event handler triggers itself and results in an infinite loop that exhausts resources. If you are calling set() or remove() within a handler, make sure it will not result in the same handler being invoked again with a new event.

Advanced options #

The primary goal of the data interface is to make interacting with your data extremely easy. However, sometimes special use cases require advanced options. Below are the current advanced capabilities available to users.

Created timestamp integrity check #

When overwriting items with the overwrite: true flag, the entire item and its meta data are replaced (including the original created timestamp). This is useful because you don't need to query the item first to replace it. However, sometimes you may want to overwrite the item, but preserve the original created timestamp. The data interface allows you to do this by setting the created value in the set method's "options" object.

The created option's value must be set to the epoch time (in seconds) of the created timestamp in the item you're overwriting. For example, if the original stored item is:

{
  key: "myKey",
  value: "some value",
  created: "2023-06-30T03:51:48.000Z",
  modified: "2023-06-30T14:15:40.000Z"
}

You would pass { overwrite: true, created: 1688097108 } to the set method's options object.

Storing null values #

By default, the data interface removes all null (and undefined) attribute values from any object or single value being stored. This is considered a best practice since storing extraneous data in NoSQL can increase storage and data transfer costs as well as potentially add latency to index replication. However, if you'd like to store null values, you can override the default behavior by adding a removeNulls:false flag to the set operation's "options" object.

If you would like to set this as a global option, you can set data.removeNulls = false after your @ampt/data import statement.

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import { data } from "@ampt/data";
data.removeNulls = false;