Add feature comparison matrix

Also update overview and faq docs.

documentation/faq.md

@@ -15,16 +15,18 @@ Liftbridge [overview](overview.md) for more information.
 
 ## Why was it created?
 
-Liftbridge was designed to bridge the gap between sophisticated log-based
-messaging systems like Apacha Kafka and Apache Pulsar and simpler, cloud-native
-systems. There is no ZooKeeper or other unwieldy dependencies, no JVM, no
-complicated API, and client libraries are just [gRPC](https://grpc.io/). More
-importantly, Liftbridge aims to extend NATS with a durable, at-least-once
-delivery mechanism that upholds the NATS tenets of simplicity, performance, and
-scalability. Unlike [NATS
+Liftbridge was designed to bridge the gap between sophisticated but complex
+log-based messaging systems like Apache Kafka and Apache Pulsar and simpler,
+cloud-native solutions. There is no ZooKeeper or other unwieldy dependencies,
+no JVM, no complicated API or configuration, and client libraries are just
+[gRPC](https://grpc.io/). More importantly, Liftbridge aims to extend NATS with
+a durable, at-least-once delivery mechanism that upholds the NATS tenets of
+simplicity, performance, and scalability. Unlike [NATS
 Streaming](https://github.com/nats-io/nats-streaming-server), it uses the core
 NATS protocol with optional extensions. This means it can be added to an
 existing NATS deployment to provide message durability with no code changes.
+The ultimate goal of Liftbridge is to provide a message-streaming solution with
+a focus on simplicity and usability. 
 
 ## Why not NATS Streaming?
 
@@ -75,11 +77,3 @@ will step up to replace it. The replication protocol closely resembles that of
 Kafka, so there is much more nuance to avoid data consistency problems. See the
 [replication protocol documentation](replication_protocol.md)
 for more details.
-
-## What about performance?
-
-*Benchmarks soon to come...*
-
-## Is it production-ready?
-
-No, this project is early and still evolving.

documentation/feature_comparison.md

@@ -0,0 +1,40 @@
+---
+id: feature-comparison
+title: Feature Comparison
+---
+
+Liftbridge shares some similarities with other stream-oriented pub/sub
+messaging systems. The below feature-comparison matrix shows how it compares to
+a few of these systems. 
+
+> **Architect's Note**
+>
+> These are highly nuanced pieces of infrastructure, so a straight comparison
+> of features is often of minimal value when evaluating solutions. This matrix
+> is primarily meant to serve as a reference point for those attempting to
+> develop a mental model of Liftbridge.
+
+|  | Liftbridge | NATS Streaming | Apache Kafka | Apache Pulsar |
+|:----|:----|:----|:----|:----|
+| Runtime | self-contained binary | self-contained binary | JVM | JVM |
+| At-least-once delivery | ✓ | ✓ | ✓ | ✓ |
+| Transactions |  |  | ✓ |  |
+| Partitioning | ✓ |  | ✓ | ✓ |
+| Linear Horizontal Scalability | ✓ |  | ✓ | ✓ |
+| Clustering/Replication | ✓ | ✓ | ✓ | ✓ |
+| External Coordination |  |  | Apache ZooKeeper | Apache ZooKeeper |
+| Message Replay | ✓ | ✓ | ✓ | ✓ |
+| Message Queueing |  | ✓ |  | ✓ |
+| Wildcard Topic Matching | ✓ | |  | |
+| Topic Pausing | ✓ | |  | |
+| Rate Limiting |  | opt-in rate matching | quotas | publish rate limiting |
+| Log Retention | ✓ | ✓ | ✓ | ✓ |
+| Log Compaction | ✓ |  | ✓ | ✓ |
+| Message Headers | ✓ |  | ✓ | ✓ |
+| Multiple Consumers | independent subscribers | queue subscriptions | consumer groups | subscriptions |
+| Consumer Position Tracking | | durable subscriptions | consumer groups | cursors |
+| Event-enabled | activity stream | | | |
+| Multitenancy | namespaced clusters | namespaced clusters | topic-level ACLs | multitenant shared cluster |
+| Authentication | TLS | User authentication, TLS | TLS, Kerberos, SASL | TLS, Kerberos, JWT, Athenz |
+| Authorization | | | ACLs | ACLs |
+| Storage | filesystem | memory, filesystem, SQL| filesystem | filesystem (Apache BookKeeper), tiered storage (Amazon S3, Google Cloud Storage) |

documentation/overview.md

@@ -27,16 +27,18 @@ messages. Unlike a message queue where consumers *remove* messages from a
 queue, with Liftbridge, consumers read back the log. In this sense, the design
 is very similar to [Apache Kafka](http://kafka.apache.org/).
 
-Liftbridge was designed to bridge the gap between sophisticated log-based
-messaging systems like Apache Kafka and Apache Pulsar and simpler, cloud-native
-systems. There is no ZooKeeper or other unwieldy dependencies, no JVM, no
-complicated API, and client libraries are just [gRPC](https://grpc.io/). More
-importantly, Liftbridge aims to extend NATS with a durable, at-least-once
-delivery mechanism that upholds the NATS tenets of simplicity, performance, and
-scalability. Unlike [NATS
+Liftbridge was designed to bridge the gap between sophisticated but complex
+log-based messaging systems like Apache Kafka and Apache Pulsar and simpler,
+cloud-native solutions. There is no ZooKeeper or other unwieldy dependencies,
+no JVM, no complicated API or configuration, and client libraries are just
+[gRPC](https://grpc.io/). More importantly, Liftbridge aims to extend NATS with
+a durable, at-least-once delivery mechanism that upholds the NATS tenets of
+simplicity, performance, and scalability. Unlike [NATS
 Streaming](https://github.com/nats-io/nats-streaming-server), it uses the core
 NATS protocol with optional extensions. This means it can be added to an
 existing NATS deployment to provide message durability with no code changes.
+The ultimate goal of Liftbridge is to provide a message-streaming solution with
+a focus on simplicity and usability.
 
 The high-level data flow in Liftbridge is shown in the diagram below.
 

website/i18n/en.json

@@ -29,6 +29,9 @@
       "faq": {
         "title": "Frequently Asked Questions"
       },
+      "feature-comparison": {
+        "title": "Feature Comparison"
+      },
       "ha-and-consistency-configuration": {
         "title": "Configuring for High Availability and Consistency"
       },
@@ -144,6 +147,7 @@
     "links": {
       "GitHub": "GitHub",
       "Docs": "Docs",
+      "Download": "Download",
       "Help": "Help"
     },
     "categories": {

website/sidebars.json

@@ -4,6 +4,7 @@
         "overview",
         "faq",
         "concepts",
+        "feature-comparison",
         "quick-start"
     ],
     "Configuration": [