How to design dApp UIs with wallets, AA, RPC fallback, reorgs?

Long Answer‍

Architecting a dApp front end for resilience across wallets, chains, and transaction states requires combining standards support (EIP-1193, ERC-4337) with a carefully layered client stack. The challenge is ensuring that users see accurate transaction status even under RPC outages or chain reorganizations.

1. Multi-wallet support (EIP-1193)
At the connection layer, follow EIP-1193 provider standard, which unifies request(), on(), removeListener(). Wrap wallets (MetaMask, WalletConnect, Coinbase Wallet, Ledger) in a provider manager that detects injected/global providers and allows users to select. Libraries like wagmi, rainbowkit, web3modal simplify detection, connection persistence, and switching chains.

2. Account abstraction (ERC-4337)
AA replaces direct txs with UserOperations relayed via bundlers. The UI must:

• Support standard JSON-RPC endpoints (eth_sendUserOperation, eth_getUserOperationReceipt).
  
• Show pending userOps separately from normal txs.
  
• Poll the bundler or indexer for userOp status, mapping to familiar states (submitted, included, confirmed).
  
• Handle paymasters (sponsored gas) gracefully in the UI.
  
  

3. RPC client & fallback strategy
RPC outages are common. Architect the front end to:

• Use multiple RPC endpoints (Infura, Alchemy, Ankr, public RPCs).
  
• Implement quorum reads: send to 2–3 providers, accept majority or fastest valid.
  
• Fallback on failure with exponential backoff.
  
• Partition by type: one endpoint for reads (blocks, state), another for writes (mempool submission).
  
• Cache static data locally to reduce RPC load.
  
  

4. Chain reorg handling
Reorgs mean blocks/tx can be “unwound.” The UI must:

• Track transaction state in three layers: pending → confirmed (N blocks) → finalized (N+M blocks) where M = safety margin.
  
• Subscribe to newHeads via websockets (or poll eth_getBlockByNumber) to detect reorgs.
  
• On mismatch (parent hash differs), reconcile: remove orphaned txs from “confirmed” and return them to “pending/unknown.”
  
• Surface UX messaging (“Transaction temporarily reorged, awaiting re-confirmation”).
  
  

5. Transaction state management
Design a tx state machine in the UI:

• Pending: after eth_sendTransaction/sendUserOperation. Show spinner.
  
• Included: tx hash appears in block.
  
• Confirmed: tx in block N, deepened past k confirmations.
  
• Finalized: beyond canonical threshold.
  Store locally (Redux/Zustand) and sync with RPCs to stay resilient.
  
  

6. UX strategies

• Show optimistic UI updates after pending submission, but mark clearly until confirmed.
  
• Provide cancel/retry flows (speed up, replace tx nonce).
  
• Use notifications/toasts for reorg rollbacks.
  
• For ERC-4337, abstract complexity: show “Transaction sent” without exposing UserOperation internals unless needed.
  
  

7. Security & integrity

• Validate RPC responses (quorum to avoid poisoned data).
  
• Handle provider disconnects (e.g., MetaMask reload).
  
• Don’t trust client-only mempool—always cross-check receipts.
  
  

8. Observability
Log wallet type, RPC latency/error rates, reorg incidents. Provide debug mode for support.

Summary:
The ideal dApp front end abstracts wallets and accounts, orchestrates multiple RPCs, and surfaces tx state with safety margins. Users see resilient, honest feedback even under reorgs or outages—critical for trust in blockchain UX.

Table

‍

Common Mistakes

(964 chars) Typical pitfalls: binding to a single RPC and showing transactions as “confirmed” after one block—leads to false confirmations after reorgs. Mixing in-memory connection state with React rerenders, losing tx context on refresh. Treating ERC-4337 UserOperations as if they were normal txs, confusing users when receipts differ. Forgetting to support provider disconnect/reconnect events (accountsChanged, chainChanged). Skipping quorum checks, trusting bad RPCs, or ignoring bundler errors. Over-optimistic UX—marking txs confirmed instantly—erodes trust. No fallback UI when wallets fail to inject providers. Not handling nonce replacement flows properly, leading to duplicates.

‍

Sample Answers (Junior / Mid / Senior)

‍Junior:
“I’d connect wallets with web3modal (EIP-1193). After sending a tx, I’d poll for the receipt until confirmed. For real-time updates, I’d subscribe to new blocks and update the UI.”

Mid:
“I’d architect a provider manager supporting multiple wallets. For reliability, I’d add fallback RPCs and show txs as pending until a few confirmations. I’d handle reorgs by rolling back confirmed txs if blocks diverge. For ERC-4337, I’d use bundler RPCs and map UserOps into normal tx states.”

Senior:
“I’d build a layered client: wallet adapter (EIP-1193), AA adapter (ERC-4337), and RPC client with quorum/fallback. Transaction state managed via a Redux machine (pending/included/confirmed/finalized) synced to block subscriptions. Chain reorgs reconcile via parent hash checks. UX: optimistic but transparent, with rollback toasts. Security: quorum validation, failover, nonce replacement flows. Observability logs RPC errors, reorg counts, and wallet events for debugging.”

‍

Evaluation Criteria (1000–1100 chars)

Interviewers assess if you can:

• Explain EIP-1193 multi-wallet handling.
  
• Integrate ERC-4337 account abstraction flows.
  
• Design RPC fallback/quorum strategies.
  
• Handle chain reorgs gracefully in the UI.
  
• Maintain an accurate tx state machine.
  
• Show user trust signals (pending/confirmed/finalized).
  
• Handle wallet disconnect/reconnect events.
  
• Consider security: bad RPC data, nonce replacement, bundler errors.
  
  

Add observability: error/reorg metrics. Weak answers: “use MetaMask only,” “one RPC,” or “mark txs confirmed after one block.” Strong answers: layered adapters, quorum fallback, explicit state machine, and resilient UX under reorgs.

‍

Preparation Tips

Build a demo dApp:

• Use wagmi/rainbowkit to support multiple wallets (EIP-1193).
  
• Integrate ERC-4337 by calling bundler RPC endpoints. Show pending → confirmed mapping.
  
• Configure multiple RPCs (Infura + Alchemy + public) in viem/ethers; add failover logic.
  
• Implement a Redux/Zustand tx state machine.
  
• Subscribe to new blocks via websockets. Detect parentHash mismatch → rollback confirmed txs.
  
• UX: optimistic updates, but mark confirmed only after 3–6 blocks. Add reorg notifications.
  
  

Test failure: shut down an RPC, trigger a reorg on a local testnet, simulate bundler failure. Practice explaining: how you isolate wallets, abstract accounts, and prevent users seeing wrong tx states.

‍

Real-world Context

A DeFi dashboard integrated 5 wallets using wagmi. Early on, it relied on one RPC (Infura); when it went down, all tx tracking failed. Switching to a quorum of Infura + Alchemy + public RPCs fixed reliability. Another project added ERC-4337 support: bundler status was polled separately, then mapped to pending/confirmed UX. A GameFi app suffered trust issues when reorgs “erased” confirmed txs; after adding block subscriptions and rollback flows, user complaints dropped 40%. A wallet provider integration broke on accountsChanged events until handled properly. These examples show that multi-wallet + AA + reorg-safe state machines are now table stakes for serious dApps.

‍

Key Takeaways

• Abstract wallets via EIP-1193 provider manager.
  
• Support ERC-4337 bundlers and map UserOps to tx states.
  
• Use multiple RPCs with quorum + fallback.
  
• Detect reorgs via block subscriptions, rollback tx state.
  
• Show clear pending → confirmed → finalized states for trust.

Practice Exercise

Scenario: You’re building a DeFi dashboard. Requirements: support MetaMask, WalletConnect, and Ledger; integrate ERC-4337 gasless txs; use multiple RPCs; and show users correct tx states even if reorgs occur.

Tasks:

1. Implement a wallet adapter layer using wagmi or custom EIP-1193 manager.
   
2. Add ERC-4337 support: send userOps to a bundler; poll receipts separately. Map them into pending → confirmed UX.
   
3. Configure viem/ethers with 3 RPCs. Implement fallback: fastest response wins, or majority quorum. Failover with exponential backoff.
   
4. Build a tx state machine in Redux: pending → included → confirmed (3 blocks) → finalized (12 blocks).
   
5. Subscribe to blocks; detect reorgs (parent hash mismatch). Roll back orphaned txs from confirmed → pending.
   
6. UX: optimistic UI updates, rollback notifications, retry/cancel flows.
   
7. Test: simulate RPC outage, inject a testnet reorg, and fail a bundler. Ensure the UI still reports accurate state.
   
   

Deliverable: Write a 2-minute walkthrough explaining how your dApp UI handles wallets, AA, fallback RPCs, and reorgs — keeping transaction state reliable.