Substreams Foundational Stores

Foundational Store architecture, components, and technical reference

A high-performance, multi-backend key-value storage system designed for Substreams ingestion and serving within the StreamingFast ecosystem. The foundational store provides a unified interface to persist and query time-series blockchain data with fork-awareness and efficient batch processing.

StreamingFast Ecosystem Integration

The foundational store operates as a critical component in the StreamingFast data processing pipeline:

• Tier1 (Substreams Frontend): Client-facing gRPC service that handles user requests, manages authentication, and orchestrates work distribution to Tier2 execution engines with foundational store endpoint routing

• Tier2 (Substreams Execution Engine): Computational backend service that executes Substreams WASM modules in parallel across blockchain data segments, handling module execution and state management

• Foundational Store: Persistent storage layer serving multiple Substreams modules simultaneously

Deployment Patterns

• Many-to-Many Architecture: Multiple Substreams modules can target the same foundational store

• Multi-Store Deployments: Multiple foundational stores can run simultaneously, each serving multiple endpoints

• Flexible Routing: Tier1 routes requests via configuration

• Module Examples: Custom Substreams modules for any blockchain data processing use case

Architecture

The foundational store consists of three main components:

• Sink: Ingests streaming data from Substreams, handles batching, flushing, and fork reorganizations

• Store: Provides a unified interface for multiple storage backends (Badger, PostgreSQL) with ForkAware caching layer

• Server: Exposes a gRPC API for data retrieval with high-performance querying and block-aware responses

Key Features

• Fork-aware storage: Handles blockchain reorganizations through ForkAware wrapper with in-memory cache and automatic rollback capabilities

• Multiple backends: Support for embedded Badger database and PostgreSQL with unified Store interface

• Block-level versioning: Every entry tagged with block number for precise historical queries and LIB-based finality

• Conditional operations: IfNotExist flag prevents duplicate insertions and ensures data integrity

• Streaming ingestion: Continuous processing of Substreams output with cursor-based resumption

• High-performance serving: gRPC API with Get/GetFirst operations and block-reached validation

Quick Start

Installation

Build from source:

git clone https://github.com/streamingfast/substreams-foundational-store
cd substreams-foundational-store
go build -o foundational-store ./cmd/foundational-store

See Hosting a Foundational Store for complete setup and configuration instructions.

Storage Backends

Badger

High-performance embedded key-value store, ideal for single-node deployments:

--dsn "badger:///path/to/database"

PostgreSQL

Enterprise-grade relational database for distributed deployments:

--dsn "postgres://user:password@host:port/database?sslmode=require"

See Hosting a Foundational Store for backend-specific configuration and tuning.

Configuration

The foundational-store binary provides the following commands:

foundational-store [command]

Available Commands:
  completion  Generate the autocompletion script for the specified shell
  get         Get a value from the foundational-store using gRPC
  help        Help about any command
  server      Start the gRPC server

See Hosting a Foundational Store for detailed server configuration options and usage examples.

Data Model

Entry Structure

Data is stored as key-value pairs with block-level versioning:

// Current v2 API (recommended)
message Entry {
  Key key = 2;
  google.protobuf.Any value = 4;
}

message Key {
  bytes bytes = 1;
}

message QueriedEntry {
  ResponseCode code = 1;
  Entry entry = 2;
}

message QueriedEntries {
  repeated QueriedEntry entries = 2;
}

// Batch operations with conditional insertion
message SinkEntries {
  repeated Entry entries = 1;
  bool if_not_exist = 2;  // Skip insertion if key already exists
}

API Operations

The Foundational Store provides gRPC APIs for data retrieval with block-aware querying.

See Consuming a Foundational Store for detailed API usage, response handling, and code examples.

Conditional Operations

The store supports conditional insertion with the if_not_exist flag for data integrity during ingestion.

See Hosting a Foundational Store for details on using SinkEntries and conditional operations.

Note: v1 API is deprecated. Use v2 API for all new implementations.

API Version History

• v2 (current): Improved service interface with Get and GetFirst operations, enhanced data models

• v1 (deprecated): Legacy interface with separate Get and GetAll operations, will be removed in a future version

Migration guide: Replace v1 service calls with v2 equivalents. Update message types to use sf.substreams.foundational_store.model.v2 and sf.substreams.foundational_store.service.v2.

Fork Handling

The foundational store implements sophisticated fork-awareness through a layered architecture:

ForkAware Store Layer

1. In-Memory Cache: Maintains recent entries in memory with block-level versioning

2. Automatic Eviction: EvictUpToBlock() removes data >= reorganization point during undo signals

3. LIB-Based Flushing: FlushUpToBlock() persists finalized entries (≤ Last Irreversible Block) to backend

4. Read Strategy: Checks cache first, falls back to persistent backend for historical data

Block Processing Flow

1. HandleBlockScopedData: Processes streaming data, updates cache, flushes finalized blocks

2. HandleBlockUndoSignal: Triggers eviction on fork detection, maintains data consistency

3. Cursor Management: Persistent state tracking with LIB-based cursor history cleanup

4. Head Block Tracking: Real-time block progression for client synchronization validation

Health Checks

Monitor service health through:

• gRPC reflection for service discovery

• Cursor file updates for ingestion progress

• Prometheus /metrics endpoint availability

Documentation

Comprehensive API documentation is available in the proto files:

• proto/sf/substreams/foundational-store/service/v2/service.proto - Current gRPC service API

• proto/sf/substreams/foundational-store/model/v2/model.proto - Data model definitions

Related Resources

• Hosting a Foundational Store - Complete guide for setting up and running a Foundational Store server

• Consuming a Foundational Store - Guide for querying Foundational Stores in Substreams modules

• Foundational Store Examples - Chain-specific foundational store implementations

• GitHub Repository - Source code and issue tracker

• Substreams - Real-time blockchain data processing

• Firehose - Blockchain data extraction protocol