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    /**
     * The {@link IsolationLevel} that every transaction created by {@link StateStore#newTransaction()} should use.
     * <p>
     * In the context of a {@link org.apache.kafka.streams.processor.StateStore} transaction, these Isolation Levels
     * adhere to the <a href="https://en.wikipedia.org/wiki/Isolation_(database_systems)#Read_phenomena">ANSI SQL 92
     * definitions</a>.
     * <p>
     * All isolation levels guarantee "read-your-own-writes", i.e. that writes in the transaction will be seen by
     * subsequent reads <em>from within the same transaction</em>. Other guarantees vary by isolation level:
     * <p>
     * <table>
     *     <tr>
     *         <th>Isolation Level</th>
     *         <th>Description</th>
     *         <th>Permitted Read Phenomena</th>
     *     </tr>
     *     <tr>
     *         <td>{@link IsolationLevel#READ_UNCOMMITTED}</td> // todo: ALOS
     *         <td>Allows queries to read writes from all ongoing transactions that have not-yet been committed.</td>
     *         <td>dirty reads, non-repeatable reads, phantom reads</td>
     *     </tr>
     *     <tr>
     *         <td>{@link IsolationLevel#READ_COMMITTED}</td> // todo: EOS
     *         <td>Allows queries to only read writes that have been committed to the StateStore. Writes by an ongoing
     *         transaction are not visible <em>until that transaction commits</em>.</td>
     *         <td>non-repeatable reads, phantom reads</td>
     *     </tr>
     * </table>
     * <p>
     * Under {@link IsolationLevel#READ_UNCOMMITTED}, there are no guarantees on when records from other transactions
     * become visible, therefore implementations <em>may</em> refrain from making uncommitted records visible to other
     * transactions until they're committed, if doing so would improve performance.
     * <p>
     * The default implementation of this method will use {@link IsolationLevel#READ_COMMITTED READ_COMMITTED} if the
     * app is {@link #appConfigs() configured} to use an {@link StreamsConfig#EXACTLY_ONCE_V2 exactly-once} {@link
     * StreamsConfig#PROCESSING_GUARANTEE_CONFIG processing guarantee}. Otherwise, it will be {@link
     * IsolationLevel#READ_UNCOMMITTED READ_UNCOMMITTED}. 
     */
    default IsolationLevel isolationLevel() {
        return StreamsConfigUtils.eosEnabled(new StreamsConfig(appConfigs())) ?
                IsolationLevel.READ_COMMITTED : IsolationLevel.READ_UNCOMMITTED;
    }