diff --git a/composer.json b/composer.json
index 03a9f8e..7afaaed 100644
--- a/composer.json
+++ b/composer.json
@@ -11,6 +11,7 @@
     "homepage": "http://amphp.org",
     "license": "MIT",
     "require": {
+        "php": ">=7",
         "amphp/amp": "^2"
     },
     "require-dev": {
diff --git a/src/AbstractPool.php b/src/AbstractPool.php
index 2d1e74c..4a4058b 100644
--- a/src/AbstractPool.php
+++ b/src/AbstractPool.php
@@ -13,6 +13,9 @@ abstract class AbstractPool implements Pool
 {
     use CallableMaker;
 
+    const DEFAULT_MAX_CONNECTIONS = 100;
+    const DEFAULT_IDLE_TIMEOUT = 60;
+
     /** @var Connector */
     private $connector;
 
@@ -28,10 +31,10 @@ abstract class AbstractPool implements Pool
     /** @var \SplObjectStorage */
     private $connections;
 
-    /** @var \Amp\Promise|null */
+    /** @var Promise|null */
     private $promise;
 
-    /** @var \Amp\Deferred|null */
+    /** @var Deferred|null */
     private $deferred;
 
     /** @var callable */
@@ -106,8 +109,8 @@ abstract class AbstractPool implements Pool
      */
     public function __construct(
         ConnectionConfig $config,
-        int $maxConnections = Pool::DEFAULT_MAX_CONNECTIONS,
-        int $idleTimeout = Pool::DEFAULT_IDLE_TIMEOUT,
+        int $maxConnections = self::DEFAULT_MAX_CONNECTIONS,
+        int $idleTimeout = self::DEFAULT_IDLE_TIMEOUT,
         Connector $connector = null
     ) {
         $this->connector = $connector ?? $this->createDefaultConnector();
@@ -136,7 +139,7 @@ abstract class AbstractPool implements Pool
                 $connection = $idle->bottom();
                 \assert($connection instanceof Link);
 
-                if ($connection->lastUsedAt() + $idleTimeout > $now) {
+                if ($connection->getLastUsedAt() + $idleTimeout > $now) {
                     return;
                 }
 
@@ -160,7 +163,7 @@ abstract class AbstractPool implements Pool
         return $this->idleTimeout;
     }
 
-    public function lastUsedAt(): int
+    public function getLastUsedAt(): int
     {
         // Simple implementation... can be improved if needed.
 
@@ -168,7 +171,7 @@ abstract class AbstractPool implements Pool
 
         foreach ($this->connections as $connection) {
             \assert($connection instanceof Link);
-            if (($lastUsedAt = $connection->lastUsedAt()) > $time) {
+            if (($lastUsedAt = $connection->getLastUsedAt()) > $time) {
                 $time = $lastUsedAt;
             }
         }
@@ -229,7 +232,7 @@ abstract class AbstractPool implements Pool
     /**
      * {@inheritdoc}
      */
-    public function getMaxConnections(): int
+    public function getConnectionLimit(): int
     {
         return $this->maxConnections;
     }
@@ -248,14 +251,14 @@ abstract class AbstractPool implements Pool
             throw new \Error("The pool has been closed");
         }
 
-        while ($this->promise !== null && $this->connections->count() + $this->pending >= $this->getMaxConnections()) {
+        while ($this->promise !== null && $this->connections->count() + $this->pending >= $this->getConnectionLimit()) {
             yield $this->promise; // Prevent simultaneous connection creation when connection count is at maximum - 1.
         }
 
         do {
             // While loop to ensure an idle connection is available after promises below are resolved.
             while ($this->idle->isEmpty()) {
-                if ($this->connections->count() + $this->pending < $this->getMaxConnections()) {
+                if ($this->connections->count() + $this->pending < $this->getConnectionLimit()) {
                     // Max connection count has not been reached, so open another connection.
                     ++$this->pending;
                     try {
@@ -409,14 +412,14 @@ abstract class AbstractPool implements Pool
     /**
      * {@inheritdoc}
      */
-    public function transaction(int $isolation = Transaction::ISOLATION_COMMITTED): Promise
+    public function beginTransaction(int $isolation = Transaction::ISOLATION_COMMITTED): Promise
     {
         return call(function () use ($isolation) {
             $connection = yield from $this->pop();
             \assert($connection instanceof Link);
 
             try {
-                $transaction = yield $connection->transaction($isolation);
+                $transaction = yield $connection->beginTransaction($isolation);
                 \assert($transaction instanceof Transaction);
             } catch (\Throwable $exception) {
                 $this->push($connection);
diff --git a/src/CommandResult.php b/src/CommandResult.php
index 046b531..b441dbd 100644
--- a/src/CommandResult.php
+++ b/src/CommandResult.php
@@ -9,5 +9,5 @@ interface CommandResult
      *
      * @return int
      */
-    public function affectedRows(): int;
+    public function getAffectedRowCount(): int;
 }
diff --git a/src/Link.php b/src/Link.php
index 5d117a3..88cf9aa 100644
--- a/src/Link.php
+++ b/src/Link.php
@@ -13,5 +13,5 @@ interface Link extends Executor
      *
      * @return Promise<Transaction>
      */
-    public function transaction(int $isolation = Transaction::ISOLATION_COMMITTED): Promise;
+    public function beginTransaction(int $isolation = Transaction::ISOLATION_COMMITTED): Promise;
 }
diff --git a/src/Pool.php b/src/Pool.php
index 2903042..98f55b5 100644
--- a/src/Pool.php
+++ b/src/Pool.php
@@ -6,9 +6,6 @@ use Amp\Promise;
 
 interface Pool extends Link
 {
-    const DEFAULT_MAX_CONNECTIONS = 100;
-    const DEFAULT_IDLE_TIMEOUT = 60;
-
     /**
      * @return Promise<Link>
      */
@@ -27,7 +24,7 @@ interface Pool extends Link
     /**
      * @return int Maximum number of connections this pool will create.
      */
-    public function getMaxConnections(): int;
+    public function getConnectionLimit(): int;
 
     /**
      * @return int Number of seconds a connection may remain idle before it is automatically closed.
diff --git a/src/PooledResultSet.php b/src/PooledResultSet.php
index 14fab65..671e00b 100644
--- a/src/PooledResultSet.php
+++ b/src/PooledResultSet.php
@@ -9,7 +9,7 @@ class PooledResultSet implements ResultSet
     /** @var ResultSet */
     private $result;
 
-    /** @var callable|null */
+    /** @var callable */
     private $release;
 
     public function __construct(ResultSet $result, callable $release)
diff --git a/src/PooledStatement.php b/src/PooledStatement.php
index c3b1087..7c53ce6 100644
--- a/src/PooledStatement.php
+++ b/src/PooledStatement.php
@@ -74,8 +74,8 @@ abstract class PooledStatement implements Statement
         return $this->statement->getQuery();
     }
 
-    public function lastUsedAt(): int
+    public function getLastUsedAt(): int
     {
-        return $this->statement->lastUsedAt();
+        return $this->statement->getLastUsedAt();
     }
 }
diff --git a/src/PooledTransaction.php b/src/PooledTransaction.php
index 67e54b3..0088860 100644
--- a/src/PooledTransaction.php
+++ b/src/PooledTransaction.php
@@ -123,13 +123,13 @@ abstract class PooledTransaction implements Transaction
         return $this->transaction && $this->transaction->isAlive();
     }
 
-    public function lastUsedAt(): int
+    public function getLastUsedAt(): int
     {
         if (!$this->transaction) {
             throw new TransactionError("The transaction has been committed or rolled back");
         }
 
-        return $this->transaction->lastUsedAt();
+        return $this->transaction->getLastUsedAt();
     }
 
     public function close()
diff --git a/src/StatementPool.php b/src/StatementPool.php
index b75aaa2..f6b7800 100644
--- a/src/StatementPool.php
+++ b/src/StatementPool.php
@@ -57,7 +57,7 @@ abstract class StatementPool implements Statement
                 $statement = $statements->bottom();
                 \assert($statement instanceof Statement);
 
-                if ($statement->lastUsedAt() + $idleTimeout > $now) {
+                if ($statement->getLastUsedAt() + $idleTimeout > $now) {
                     return;
                 }
 
@@ -113,7 +113,7 @@ abstract class StatementPool implements Statement
      */
     protected function push(Statement $statement)
     {
-        $maxConnections = $this->pool->getMaxConnections();
+        $maxConnections = $this->pool->getConnectionLimit();
 
         if ($this->statements->count() > ($maxConnections / 10)) {
             return;
@@ -160,7 +160,7 @@ abstract class StatementPool implements Statement
     }
 
     /** {@inheritdoc} */
-    public function lastUsedAt(): int
+    public function getLastUsedAt(): int
     {
         return $this->lastUsedAt;
     }
diff --git a/src/TransientResource.php b/src/TransientResource.php
index 20f55bc..3eb5fa4 100644
--- a/src/TransientResource.php
+++ b/src/TransientResource.php
@@ -14,7 +14,7 @@ interface TransientResource
     /**
      * Get the timestamp of the last usage of this resource.
      *
-     * @return int
+     * @return int Unix timestamp in seconds.
      */
-    public function lastUsedAt(): int;
+    public function getLastUsedAt(): int;
 }
diff --git a/test/StatementPoolTest.php b/test/StatementPoolTest.php
index 6d433a0..7005dd9 100644
--- a/test/StatementPoolTest.php
+++ b/test/StatementPoolTest.php
@@ -36,14 +36,14 @@ class StatementPoolTest extends TestCase
                 ->getMockForAbstractClass();
 
             $this->assertTrue($statementPool->isAlive());
-            $this->assertSame(\time(), $statementPool->lastUsedAt());
+            $this->assertSame(\time(), $statementPool->getLastUsedAt());
 
             yield new Delayed(1500); // Give timeout watcher enough time to execute.
 
             $statementPool->execute();
 
             $this->assertTrue($statementPool->isAlive());
-            $this->assertSame(\time(), $statementPool->lastUsedAt());
+            $this->assertSame(\time(), $statementPool->getLastUsedAt());
         });
     }
 
@@ -72,7 +72,7 @@ class StatementPoolTest extends TestCase
                 ->getMockForAbstractClass();
 
             $this->assertTrue($statementPool->isAlive());
-            $this->assertSame(\time(), $statementPool->lastUsedAt());
+            $this->assertSame(\time(), $statementPool->getLastUsedAt());
 
             $statementPool->execute();
 
@@ -81,7 +81,7 @@ class StatementPoolTest extends TestCase
             $statementPool->execute();
 
             $this->assertTrue($statementPool->isAlive());
-            $this->assertSame(\time(), $statementPool->lastUsedAt());
+            $this->assertSame(\time(), $statementPool->getLastUsedAt());
         });
     }
 }