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FireScroll 🔥📜

The config database to deploy everywhere, without the complexity of other multi region dbs.

A highly available multi-region config database for massive read scalability with a focus on low latency and high concurrency. Have replicas in any number of regions without impacting write or read performance of other nodes.

Perfect for config management in all regions. Serve sub-ms reads from disk to your APIs and services in the same datacenter.

Useful cases that can tolerate sub-second cache-like behavior such as:

  • DNS providers serving DNS records
  • Webhost routing (e.g. Vercel mapping your urls to your files and functions)
  • Feature flagging and A/B testing
  • SSL certificate serving
  • CDN configs
  • ML model feature store
  • and many more!

FireScroll tackles a very specific use-case, and is meant to be used in addition to a traditional OLTP DB like CockroachDB or Scylla.


  • Quick durability of linearizable writes with decoupled read throughput
  • Arbitrary number of read replicas supported
  • Serves global low latency reads (300-700us for <1KB documents) with high concurrency
  • Remote partition proxying for reads
  • Conditional (If) statements checked at mutation time
  • No need to peer regions, only the Kafka cluster needs to be accessible from other regions

Quick Notes

This Readme is still a WIP, and so is this project. If you see any areas of improvement please open an issue!

I would not call this "production ready" in the traditional sense, as it lacks extensive automated testing.

Redpanda and Kafka are used pretty interchangeably here. They mean the same thing, and any differences (e.g. configuration properties) will be noted.


The API is HTTP/1.1 & 2 compatible, with all operations as a POST request and JSON bodies.

See examples in records.http

Put Record(s) POST /records/put

Get Record(s) POST /records/get

Delete Record(s) POST /records/delete

List Records POST /records/list


option description
pk Required, the partition key to list over.
limit The max number of records to return. A value of 0 means no limit, be careful of memory usage. Default 0.
sk_prefix Start at a certain sk prefix. Can be a partial or entire sort key. If sk_prefix == sk, the record will be skipped. This is so that it can be used to continue sorting from where you left off.
if Conditional in which records will either be omitted, or listing will stop. Default omitted, controlled by if_stop. Must be >= 0, default 0. If 0, then no limit. Be careful about out-of-memory errors.
if_stop If true, then once the if condition fails (if provided) then listing will stop. Useful for only listing a given prefix, and preventing over-listing.

The example requests in records.http provide many use cases based on the test data.

(WIP) Batch Put and Delete Records POST /records/batch

Multiple Put and Delete operations can be sent in a single request, which will result in all operations being atomic.

If any condition fails, then all operations will be aborted

Quick Start (running locally)

The first step is to create the following topics in Kafka:

  1. firescroll_{namespace}_mutations
  2. firescroll_{namespace}_partitions

Mutations Topic

The mutations topic is used to manage all mutations (Put and Delete) that are applies to the data. It is important to set this to a partition count that is sufficient for your scale, as this cannot be changed later (nodes will refuse to start as they no longer know where data exists in). With Redpanda a partition is pretty powerful, so using are relatively high number (a few partitions per core) will cover you for a long time. For production at scale put as many topics as cores you ever intend to have in the Redpanda cluster.

For example, if you are using Redpanda it might look like:

rpk topic create firescroll_testns_mutations
rpk topic add-partitions firescroll_testns_mutations --num 3 # using 4 total partitions
rpk topic create firescroll_testns_partitions

Partitions Topic

The partitions topic is used to record the first found topic count, and allows nodes to check against this count so that they can crash if something changes (because now we don't know where data is). While the actual partitions are checked against in real time, this serves as an extra dummy check in case you change the partition count and update the env vars (since data is not currently re-partitioned). So it's just an extra redundancy check and only ever (intentionally) writes one record, and otherwise is read on node startup.

This only needs to have one partition.

Run with Docker compose:

docker compose up -d

Then get and replace minio keys in the AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY env vars for firescroll-1 and firescroll-2 by visiting http://localhost:9001 and creating credentials in the Minio dashboard to use with the bucket testbucket that was automatically created.

Run with a local build:


  1. Go
  2. Taskfile
  3. Docker

To run locally:


This will start Redpanda and Minio, and set up the topics with the namespace testns.

From there go to http://localhost:9001 and create a key pair in Minio to use with the bucket testbucket that was automatically created.

Take the keys for Minio, and copy the .env.local file to .env, replacing my local dev keys.

You can then use task to run the first node. This will initially grab all partitions. You can make mutations inside of records.http to see mutations being written to the node's disk.

You can then run task 2 to bring up another node and watch as the partitions get rebalanced, and the new node restores from S3. If you make more get requests you will see in the logs that they are proxied to the other partition!


Delete the dbs and dbs2 folder, and run:


to clean up the docker compose volumes.


For all options, see env.go. Here are some notable ones:

Env Var Description Type
NAMESPACE global, should be the same for all regions string
REPLICA_GROUP per replica in a region, maps to a Kafka consumer group. A replica group should only exist in one region, never spanning regions. string
INSTANCE_ID unique to the node string
TOPIC_RETENTION_MS configured in Kafka, but FireScroll needs to know for backup management! (WIP for warnings) int
PARTITIONS do not change this once you start consuming mutations. FireScroll will do it's best to refuse to work if it detects a change so data is not lost int
GOSSIP_PEERS CSV of (domain/ip):port for gossip peers. If omitted then GET request for other partitions will be ignored. These should only be peers within the same region (but all replica groups in a region), never across regions. You only need to list a few nodes in the region, as they discover the rest of the cluster once joined. You want all nodes within a region to be in the region's gossip cluster. string (optional)
GOSSIP_BROADCAST_MS How frequently to broadcast gossip messages. This is only the partition ownership messages, not the protocol-level messages such as heartbeats. Default 1000. int
KAFKA_SEEDS CSV of (domain/ip):port for the Kafka node seeds. string
KAFKA_TLS int 1 to enable, turns on TLS support for Kafka connections
KAFKA_USER string Username for scram SHA256 auth, must also use KAFKA_PASS for it to be used
KAFKA_PASS string Password for scram SHA256 auth, must also use KAFKA_USER for it to be used
ADVERTISE_ADDR The address to advertise to gossip peers string
BACKUP Whether to enable backups. Should choose at most 1 replica group per region. Should be same for all nodes in replica group. Set to 1 to enable. int
S3_RESTORE Whether to restore from S3 backups. Set to 1 to enable. int
AWS_REGION For S3. Use us-east-1 for local Minio string
S3_ENDPOINT The HTTP endpoint for S3. Like or If http:// SSL is automatically disabled. string
BACKUP_INTERVAL_SEC How long in seconds between backups. Default 12 hours. int
DB_PATH Where to store Badger DB files. Default /var/firescroll/dbs string
REGION Required. Region that this node is located in. Used to create a unique consumer group for region + replica group. string

You can also see example values used for local development in .env.local, and overrides for a second node in Taskfile.yaml.

The if statement

Put and Delete can all take an optional if condition that will determine whether the operation is applied at the time that a node consumes the mutation. If in a batch, then any failing If statement will revoke the whole batch.

The if condition must evaluate to a boolean (true or false), and is in expr syntax.

The available top-level keys are:

  1. pk
  2. sk
  3. data (the top level JSON object, e.g. {"key": "val"} could be checked like data.key == "val")
  4. _created_at - an internal column created when the record is first inserted, in unix ms. This is the time that the log received the mutation.
  5. _updated_at - an internal column that is updated any time the record is updated, in unix ms. This is the time that the log received the mutation.

If an If statement exists, the row will be loaded into the query engine.

There is a performance penalty to using the if statement, btu it's on the order of hundreds of microseconds per record.

Checking whether a mutation applied

The best way to check for whether a mutation applied is to have some random ID that you update for every put, and poll the lowest latency region to check if that change is applied. For deletes you can obviously check for the absence of the record.


See examples in records.http

Note: null and nil can be used interchangeably

Checking whether the key hey == ho

  "Records": [
      "pk": "pk1",
      "sk": "sk1",
      "data": {
        "hey": "no longer ho"
      "if": "data.hey == \"ho\""

This will only apply the mutation if data has this:

  "hey": "ho"

Scaling the cluster

Nodes are always members of a single replica group, but may contain multiple partitions. The partition mapping is managed by the log (Redpanda/Kafka), but you determine the replica group on boot with the REPLICA_GROUP={replica group name} env var.

Each replica group will have a single copy of all partitions.

More details are available in this section.

You can scale in multiple ways, depending on what dimension is the bottleneck:

  1. Scaling the number of nodes within a replica group
  2. Scaling the number of replica groups
  3. Scaling resources for the nodes
  4. Scaling the log

The suggested order of operations is to first create replicas (benefit of HA), then scale the nodes up, then create more nodes to spread out partitions. If your workload only ever reads from a single parititon at a time, you can look to add more nodes before scaling nodes up.

Scaling the replica group

My increasing the number of nodes in a replica group, you spread out the partitions among more nodes. With fewer partitions to manage, a node will generally receive less traffic.

Simply increase the number of nodes with the same REPLICA_GROUP env var to scale up, or decrease to scale down. The cluster will automatically adjust and rebalance.

Note: Scaling down with only a single replica group will result in temporary downtime for the partitions that were on the terminated node. Having multiple replicas avoids unavailablity.

Scaling the number of replica groups

Within the same region, you can also add replica groups to increase the number of replicas for partitions. By addition an addition replica group, you are adding a copy of all partitions for the namespace.

This becomes a second method for scaling read performance in the cluster, as adding more replicas means more read throughput. READ and LIST operations will be routed randomly to a known replica of a partition, so scaling the replicas provides linear scaling of read throughput.

It also increases the availability of the cluster as any replica of a partition can serve a read.

Scaling resources for the nodes

Nodes will utilize all resources for read performance, so more cores and memory = faster performance.

Scaling the log

If you saturate the resources of the log (Redpanda/Kafka) cluster, you may need to scale up those nodes as well. Monitor the network traffic and CPU usage to determine this.

Topic Management


This will break the namespace if you do not know exactly what you are doing.

When a namespace is created, 2 topic within Kafka are created: firescroll_{namespace}_mutations and firescroll_{namespace}_partitions.


The mutations topic is used for streaming the KV operations to the storage nodes. This should have a configured retention that is far beyond what a disaster recovery scenario might look like (e.g. 7 days).


The partition topic is used to record the number of partitions when the namespace is created. This topic must have unlimited retention, and only a single record is placed in (optimistically). This ensures that we can enforce that the number of partitions cannot change.

On start, a node will read from this topic and check against its configured number of partitions. If they differ for any reason, then the node will refuse to start. If a node inserts a record (due to the topic not existing or being empty), then it will verify by waiting until it can consume the first record in the topic. If a node fails to create a topic because it already exists, but there are no records yet, it will insert its partition count in. If a race condition occurs where multiple nodes start with different partition counts, only one partition count will be established, and other nodes will fail to initialize.

Since the number of partitions cannot be changed, by default it is a high value of 256. This should cover all the way up to the most absurd scales, as you can continue to increase replicas and per-node resources.

Backups and Snapshotting

Backups are also used as snapshots for partition-shuffling. When a partition is remapped to another node (either via scaling or recovery), the node will first restore the partition from a remote S3 backup. It will then reset the partition checkpoint to the time of the backup, and consume the log from there. This results in a faster recovery, and the topic can expire records over time, preventing unbound log growth.

Backups can be explicitly enabled with BACKUP=true env var. Backups should be enabled at the replica-group level, and all nodes within the same replica group should have the same BACKUP value. Backups are named via the partition, so distinct regions should use distinct buckets if you plan on having multiple backup replica groups.

This allows for multiple backup strategies such as:

  1. A single replica group in a single region is marked for backing up, and other groups and regions point to that S3 path for restore. This results in less redundancy, but less bandwidth and storage used
  2. A single replica group in each region is marked, and the local region points to that. This results in more redundancy and faster restores, but increased storage usage and bandwidth.

You should choose a strategy depending on your needs.

There are multiple env vars to use for this functionality such as:



With FireScroll you perform mutations (put, delete) to a centralized log cluster powered by Kafka, which partitions and streams those changes to FireScroll nodes deployed in all of the same data centers as your logical compute (API, services, etc). You read from FireScroll nodes within the same data center to ensure you have the lowest possible latency lookups, while also ensuring that all mutation operations are linearizable.

See the intro blog post here for a more detailed look at the architecture.

Briefly, this database turns the traditional DB inside-out: Rather than having multiple nodes with each their own WAL, a distributed central WAL cluster is used (Kafka/Redpanda) and nodes consume from that, materializing to disk and backing that snapshot of the log to S3 so that they can be restored on other nodes (during partition remapping) without needing to consume the entire WAL history (this is specifically important for allowing us to have a really short retention period on the WAL!)

This allows us to decouple reads and writes, meaning that nodes in different regions can consume at their own pace. For example the latencies of servers in Japan do not affect the write performance of servers in North Virginia. This also removes the issue found in Cassandra of the possibility of entering a permanently inconsistent state between replicas of partitions, requiring repairs. It also means that nodes are not responsible for coordinating replication, allowing them to focus on serving reads fast.

It uses Kafka or Redpanda as the distributed WAL (prefer Redpanda), and Badger as the local KV db. A single node can easily serve reads in the hundreds of thousands per second.

This arch also enables arbitrary number of read replicas for increased performance, or adding more nodes to spread out the partitions. While it does enable sub-ms reads (typically 300-700us for <1KB documents), it focuses more on concurrency. Under load, FireScroll will favor concurrency over latency due to the locking techniques employed. Reads are also prioritized over mutations.

It's also extremely easy to manage. By having a 2-tier architecture (Kafka -> Nodes) there is no complex cascading replication.

Backups to S3 are also used to aid in partition remapping and bringing new replicas online, allowing the Kafka log to be keep a low retention without losing data.


This section is still WIP, and may no longer be relevant as optimizations are made. Always do performance tests for your use cases in your environment for more accurate numbers.

Even with ~1000 requests per second running on a laptop, FireScroll is able to keep p98 of get requests <1ms and p99.99 of partition operations <1ms, with most requests happening under 400us. Every request was pulling 2 records, each from their own partition:

# HELP http_latencies_micro Full HTTP request processing latencies. Includes remote lookups for gets.
# TYPE http_latencies_micro histogram
http_latencies_micro_bucket{operation="get",le="100"} 0
http_latencies_micro_bucket{operation="get",le="200"} 122
http_latencies_micro_bucket{operation="get",le="300"} 3353
http_latencies_micro_bucket{operation="get",le="400"} 11920
http_latencies_micro_bucket{operation="get",le="500"} 16459
http_latencies_micro_bucket{operation="get",le="750"} 17980
http_latencies_micro_bucket{operation="get",le="1000"} 18121
http_latencies_micro_bucket{operation="get",le="1250"} 18177
http_latencies_micro_bucket{operation="get",le="1500"} 18216
http_latencies_micro_bucket{operation="get",le="2000"} 18296
http_latencies_micro_bucket{operation="get",le="2500"} 18333
http_latencies_micro_bucket{operation="get",le="3000"} 18360
http_latencies_micro_bucket{operation="get",le="4000"} 18425
http_latencies_micro_bucket{operation="get",le="5000"} 18456
http_latencies_micro_bucket{operation="get",le="6000"} 18484
http_latencies_micro_bucket{operation="get",le="10000"} 18538
http_latencies_micro_bucket{operation="get",le="15000"} 18580
http_latencies_micro_bucket{operation="get",le="+Inf"} 18649
http_latencies_micro_sum{operation="get"} 1.2027937e+07
http_latencies_micro_count{operation="get"} 18649
# HELP partition_operation_latencies_micro Latencies for partition-level operations in microseconds
# TYPE partition_operation_latencies_micro histogram
partition_operation_latencies_micro_bucket{operation="get",le="10"} 1961
partition_operation_latencies_micro_bucket{operation="get",le="15"} 11391
partition_operation_latencies_micro_bucket{operation="get",le="25"} 16730
partition_operation_latencies_micro_bucket{operation="get",le="50"} 26409
partition_operation_latencies_micro_bucket{operation="get",le="75"} 34313
partition_operation_latencies_micro_bucket{operation="get",le="100"} 36529
partition_operation_latencies_micro_bucket{operation="get",le="200"} 37250
partition_operation_latencies_micro_bucket{operation="get",le="300"} 37273
partition_operation_latencies_micro_bucket{operation="get",le="400"} 37279
partition_operation_latencies_micro_bucket{operation="get",le="500"} 37282
partition_operation_latencies_micro_bucket{operation="get",le="750"} 37285
partition_operation_latencies_micro_bucket{operation="get",le="1000"} 37287
partition_operation_latencies_micro_bucket{operation="get",le="1250"} 37288
partition_operation_latencies_micro_bucket{operation="get",le="1500"} 37289
partition_operation_latencies_micro_bucket{operation="get",le="2000"} 37289
partition_operation_latencies_micro_bucket{operation="get",le="2500"} 37289
partition_operation_latencies_micro_bucket{operation="get",le="3000"} 37289
partition_operation_latencies_micro_bucket{operation="get",le="+Inf"} 37290
partition_operation_latencies_micro_sum{operation="get"} 1.417517e+06
partition_operation_latencies_micro_count{operation="get"} 37290

As you can tell in the difference between HTTP handler and Partition-level performance, there are plenty of optimization opportunities!

There is also plenty of optimization to be had by using a more efficient serialization format and serializer (default Go JSON is known to be slow), collapsing requests to remote partitions, and more!

The extreme performance of partition-level operations illuminates how the system optimizes for concurrency and stays performant under load, as very little time is actually spent competing for storage. 32 region test

Admittedly not the greatest scale test in the world (was quick and dirty), so don't read too much into this 😅.

A test was run 50 nodes across in 32 regions around the world on Every region had at least 1 node, some had 2. Nodes each managed 3 partitions, and 2 tests were performed:

  1. Reading 3 records, each from a different partition in one read request
  2. Read a single record (1 partition)

Each node was a performance-2x (2vCPU, 4GB ram) size.


firescroll-fly.jpg firescroll-cpu

Due to account limits I was only able to load it up to ~225 req/s per node from my laptop, as I wanted to use all nodes possible to run FireScroll and observe the behavior of high node counts.

Some immediate observations:

  1. disks are relatively high latency (my 2019 MBP p99 partition latencies are <75us)
  2. Restricting the resources available increases latencies. On my 2019 MBP with 16 threads and 64GB ram I observed p99 get ~1.2ms
  3. Fetching more records at once increases HTTP latency but reduces per-partition latency (this is predictable). You can see where I switched the test from fetching 3 records to 1 record.
  4. Performance is still very good even when virtualized, no memory caching, and on fewer resources
  5. CPU usage remained very low despite significant load

I would like to write a test that focuses on high node counts within a single region, with large replica groups. This is a more realistic test as regions don’t talk to each other, so we can test how requests are distributed in a high-density scenario.

Follow this issue for progress on that!

Recommended Redpanda/Kafka Settings

Make sure that the group_max_session_timeout_ms and group_min_session_timeout_ms range in Redpanda (Kafka uses . instead of _) allows for your KAFKA_SESSION_MS env var value (default 60000). Redpanda uses a 30000 max so it will need to be adjusted.

Note on Upstash

Upstash does not expose access to their admin API, and therefore FireScroll cannot be used with Upstash. The Kafka admin API is required so that we can discover partition mappings, and without access we cannot know what partitions the current node is mapped to.


The config database to deploy everywhere. A highly available multi-region KV database for massive read concurrency and low latency.







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