papers/lux-gchain-graphql/sections/03-g-chain-architecture.tex

\section{G-Chain Architecture}


\subsection{System Overview}

\begin{figure}[h]
\centering
\begin{verbatim}
+--------------------------------------------------------------+
|                    G-Chain Architecture                       |
+-----------------------+--------------------------------------+
|   Storage Layer       |        Query Layer                   |
+-----------------------+--------------------------------------+
| * BadgerDB backend    | * GraphVM interpreter                |
| * Verkle trie commits | * GraphQL compiler                   |
| * Cross-chain refs    | * Gas metering                       |
| * Selective sync      | * Result serialization               |
+-----------------------+--------------------------------------+
             v                           v
    +-----------------+         +-------------------+
    |  EVM Integration|         |  External Access  |
    +-----------------+         +-------------------+
    | * Precompiles   |         | * GraphQL HTTP    |
    |   (0x0B-0x11)   |         | * WebSocket       |
    | * On-chain      |         | * ZAP wire        |
    |   queries       |         | * Client SDKs     |
    +-----------------+         +-------------------+
\end{verbatim}
\caption{G-Chain architectural layers}
\end{figure}

\subsection{Core Components}

\subsubsection{GraphDB Backend (lux/graphdb)}

BadgerDB-based storage with blockchain-specific optimizations:

\begin{lstlisting}[language=Go, basicstyle=\small\ttfamily]
type GraphDB struct {
    db       *badger.DB
    verkle   *verkle.Trie
    chainMap map[ChainID]*ChainIndex
    
    // Horizontal scaling
    syncMode    SyncMode  // Full/Chain/App-specific
    chainFilter []ChainID // Selective sync
    
    // Custom indexing
    customIndexes map[string]*Index
}

// Key-value model
// Nodes: Node:<chain>:<type>:<id>
// Edges: Edge:<chain>:<src_type>:<src_id>:<relation>:<dst>
// XRefs: XRef:<src_chain>:<dst_chain>:<id>
\end{lstlisting}

\subsubsection{GraphVM Interpreter (luxfi/graphql)}

Compiles GraphQL queries to bytecode with gas metering:

\begin{lstlisting}[language=Go, basicstyle=\small\ttfamily]
type GraphVM struct {
    compiler *Compiler
    executor *Executor
    gasMeter *GasMeter
}

// Bytecode instruction set
type OpCode uint8
const (
    OP_LOAD_NODE    OpCode = 0x01  // 100 gas
    OP_TRAVERSE     OpCode = 0x02  // 50 gas per edge
    OP_FILTER       OpCode = 0x03  // 20 gas per comparison
    OP_AGGREGATE    OpCode = 0x04  // 500 gas
    OP_JOIN         OpCode = 0x05  // 200 gas per join
)
\end{lstlisting}

\subsubsection{EVM Precompiles}

\begin{table}[h]
\centering
\begin{tabular}{@{}llr@{}}
\toprule
\textbf{Address} & \textbf{Function} & \textbf{Gas Cost} \\ \midrule
0x0B & AddNode & 50,000 + size \\
0x0C & UpdateNode & 30,000 + size \\
0x0D & DeleteNode & 20,000 \\
0x0E & AddEdge & 40,000 \\
0x0F & UpdateEdge & 25,000 \\
0x10 & DeleteEdge & 15,000 \\
0x11 & VerifyProof & 80,000 + depth \\ \bottomrule
\end{tabular}
\caption{G-Chain EVM precompile gas costs}
\end{table}