diff --git a/server/app/com/xsn/explorer/data/anorm/BalancePostgresDataHandler.scala b/server/app/com/xsn/explorer/data/anorm/BalancePostgresDataHandler.scala
new file mode 100644
index 0000000..e8bd330
--- /dev/null
+++ b/server/app/com/xsn/explorer/data/anorm/BalancePostgresDataHandler.scala
@@ -0,0 +1,21 @@
+package com.xsn.explorer.data.anorm
+
+import javax.inject.Inject
+
+import com.xsn.explorer.data.anorm.dao.BalancePostgresDAO
+import com.xsn.explorer.errors.BalanceUnknownError
+import com.xsn.explorer.models.Balance
+import org.scalactic.{One, Or}
+import play.api.db.Database
+
+class BalancePostgresDataHandler @Inject() (
+    override val database: Database,
+    balancePostgresDAO: BalancePostgresDAO)
+    extends AnormPostgresDataHandler {
+
+  def upsert(balance: Balance) = withConnection { implicit conn =>
+    val maybe = balancePostgresDAO.upsert(balance)
+
+    Or.from(maybe, One(BalanceUnknownError))
+  }
+}
diff --git a/server/app/com/xsn/explorer/data/anorm/dao/BalancePostgresDAO.scala b/server/app/com/xsn/explorer/data/anorm/dao/BalancePostgresDAO.scala
new file mode 100644
index 0000000..baf38d6
--- /dev/null
+++ b/server/app/com/xsn/explorer/data/anorm/dao/BalancePostgresDAO.scala
@@ -0,0 +1,31 @@
+package com.xsn.explorer.data.anorm.dao
+
+import java.sql.Connection
+
+import anorm._
+import com.xsn.explorer.data.anorm.parsers.BalanceParsers._
+import com.xsn.explorer.models.Balance
+
+class BalancePostgresDAO {
+
+  def upsert(balance: Balance)(implicit conn: Connection): Option[Balance] = {
+    SQL(
+      """
+        |INSERT INTO balances
+        |  (address, received, spent, available)
+        |VALUES
+        |  ({address}, {received}, {spent}, {available})
+        |ON CONFLICT (address) DO UPDATE
+        |  SET received = balances.received + EXCLUDED.received,
+        |      spent = balances.spent + EXCLUDED.spent,
+        |      available = balances.available + EXCLUDED.available
+        |RETURNING address, received, spent
+      """.stripMargin
+    ).on(
+      'address -> balance.address.string,
+      'received -> balance.received,
+      'spent -> balance.spent,
+      'available -> balance.available
+    ).as(parseBalance.singleOpt).flatten
+  }
+}
diff --git a/server/app/com/xsn/explorer/data/anorm/parsers/BalanceParsers.scala b/server/app/com/xsn/explorer/data/anorm/parsers/BalanceParsers.scala
new file mode 100644
index 0000000..c5e9da1
--- /dev/null
+++ b/server/app/com/xsn/explorer/data/anorm/parsers/BalanceParsers.scala
@@ -0,0 +1,16 @@
+package com.xsn.explorer.data.anorm.parsers
+
+import anorm.SqlParser._
+import anorm._
+import com.xsn.explorer.models.{Address, Balance}
+
+object BalanceParsers {
+
+  val parseAddress = str("address").map(Address.from)
+  val parseReceived = get[BigDecimal]("received")
+  val parseSpent = get[BigDecimal]("spent")
+
+  val parseBalance = (parseAddress ~ parseReceived ~ parseSpent).map { case address ~ received ~ spent =>
+    address.map { Balance(_, received, spent) }
+  }
+}
diff --git a/server/app/com/xsn/explorer/errors/balanceErrors.scala b/server/app/com/xsn/explorer/errors/balanceErrors.scala
new file mode 100644
index 0000000..4cfaa9e
--- /dev/null
+++ b/server/app/com/xsn/explorer/errors/balanceErrors.scala
@@ -0,0 +1,13 @@
+package com.xsn.explorer.errors
+
+import com.alexitc.playsonify.models.{PublicError, ServerError}
+import play.api.i18n.{Lang, MessagesApi}
+
+sealed trait BalanceError
+
+case object BalanceUnknownError extends BalanceError with ServerError {
+
+  override def cause: Option[Throwable] = None
+
+  override def toPublicErrorList(messagesApi: MessagesApi)(implicit lang: Lang): List[PublicError] = List.empty
+}
diff --git a/server/app/com/xsn/explorer/models/Balance.scala b/server/app/com/xsn/explorer/models/Balance.scala
new file mode 100644
index 0000000..6281526
--- /dev/null
+++ b/server/app/com/xsn/explorer/models/Balance.scala
@@ -0,0 +1,9 @@
+package com.xsn.explorer.models
+
+case class Balance(
+    address: Address,
+    received: BigDecimal = BigDecimal(0),
+    spent: BigDecimal = BigDecimal(0)) {
+
+  def available: BigDecimal = received - spent
+}
diff --git a/server/conf/evolutions/default/2.sql b/server/conf/evolutions/default/2.sql
new file mode 100644
index 0000000..0155042
--- /dev/null
+++ b/server/conf/evolutions/default/2.sql
@@ -0,0 +1,37 @@
+
+# --- !Ups
+
+-- we pre-compute the balances while storing transactions in order to perform
+-- simpler queries while requiring addresses and the available amounts.
+CREATE TABLE balances(
+  address VARCHAR(34) NOT NULL,
+  received DECIMAL(30, 15) NOT NULL,
+  spent DECIMAL(30, 15) NOT NULL,
+  available DECIMAL(30, 15) NOT NULL,
+  -- constraints
+  CONSTRAINT balances_address_pk PRIMARY KEY (address),
+  CONSTRAINT balances_address_format CHECK (address ~ '[a-zA-Z0-9]{34}$')
+  -- TODO: useful to add them if we can support them
+--  CONSTRAINT balances_available_check CHECK (available = received - spent),
+--  CONSTRAINT balances_received_ge_spent_check CHECK (received >= spent),
+--  CONSTRAINT balances_received_positive_check CHECK (received >= 0),
+--  CONSTRAINT balances_spent_positive_check CHECK (spent >= 0)
+);
+
+CREATE INDEX balances_available_index ON balances (available);
+
+
+-- there are certain addresses that we need to hide from public, like the one
+-- used for the coin swap.
+CREATE TABLE hidden_addresses(
+  address VARCHAR(34) NOT NULL,
+  -- constraints
+  CONSTRAINT hidden_addresses_address_pk PRIMARY KEY (address),
+  CONSTRAINT hidden_addresses_address_format CHECK (address ~ '[a-zA-Z0-9]{34}$')
+);
+
+
+# --- !Downs
+
+DROP TABLE hidden_addresses;
+DROP TABLE balances;
diff --git a/server/test/com/xsn/explorer/data/BalancePostgresDataHandlerSpec.scala b/server/test/com/xsn/explorer/data/BalancePostgresDataHandlerSpec.scala
new file mode 100644
index 0000000..cc61b43
--- /dev/null
+++ b/server/test/com/xsn/explorer/data/BalancePostgresDataHandlerSpec.scala
@@ -0,0 +1,114 @@
+package com.xsn.explorer.data
+
+import com.xsn.explorer.data.anorm.BalancePostgresDataHandler
+import com.xsn.explorer.data.anorm.dao.BalancePostgresDAO
+import com.xsn.explorer.data.common.PostgresDataHandlerSpec
+import com.xsn.explorer.helpers.DataHelper
+import com.xsn.explorer.models.Balance
+import org.scalactic.Good
+
+class BalancePostgresDataHandlerSpec extends PostgresDataHandlerSpec {
+
+  lazy val dataHandler = new BalancePostgresDataHandler(database, new BalancePostgresDAO)
+
+  "upsert" should {
+    "create an empty balance" in {
+      val address = DataHelper.createAddress("XxQ7j37LfuXgsLd5DZAwFKhT3s2ZMkW85F")
+      val balance = Balance(address)
+
+      val result = dataHandler.upsert(balance)
+      result mustEqual Good(balance)
+    }
+
+    "set the available amount" in {
+      val address = DataHelper.createAddress("Xbh5pJdBNm8J9PxnEmwVcuQKRmZZ7DkpcF")
+      val balance = Balance(address, received = BigDecimal(10), spent = BigDecimal(5))
+
+      val result = dataHandler.upsert(balance)
+      result mustEqual Good(balance)
+      database.withConnection { implicit conn =>
+        val available = _root_.anorm
+            .SQL(s"SELECT available FROM balances WHERE address = '${address.string}'")
+            .as(_root_.anorm.SqlParser.get[BigDecimal]("available").single)
+
+        available mustEqual balance.available
+      }
+    }
+
+    "update an existing balance" in {
+      val address = DataHelper.createAddress("XfAATXtkRgCdMTrj2fxHvLsKLLmqAjhEAt")
+      val initialBalance = Balance(address, received = BigDecimal(10), spent = BigDecimal(5))
+      val patch = Balance(address, received = BigDecimal(10), spent = BigDecimal(10))
+      val expected = combine(initialBalance, patch)
+
+      dataHandler.upsert(initialBalance)
+
+      val result = dataHandler.upsert(patch)
+      result mustEqual Good(expected)
+    }
+
+    "allow to set received coins and then, spend them all" in {
+      pending // TODO: remove it when database checks are enabled
+      val address = DataHelper.createAddress("XjfNeGJhLgW3egmsZqdbpCNGfysPs7jTNm")
+      val initialBalance = Balance(address, received = BigDecimal(10))
+      val patch = Balance(address, spent = BigDecimal(10))
+      val expected = combine(initialBalance, patch)
+
+      dataHandler.upsert(initialBalance).isGood mustEqual true
+
+      val result = dataHandler.upsert(patch)
+      result mustEqual Good(expected)
+    }
+
+    "fail to set received as negative" in {
+      pending // TODO: remove it when database checks are enabled
+      val address = DataHelper.createAddress("XdhDFQBfk4E7GE3GVRe4X1bzxiyxRiN2kr")
+      val balance = Balance(address, received = BigDecimal(-1))
+
+      val result = dataHandler.upsert(balance)
+      println(result)
+      result.isBad mustEqual true
+    }
+
+    "fail to set spent as negative" in {
+      pending // TODO: remove it when database checks are enabled
+      val address = DataHelper.createAddress("Xry2cCLNDMqLmENGW49vYJZPXHPgpqDZ8K")
+
+      val balance = Balance(address, spent = BigDecimal(-1))
+
+      val result = dataHandler.upsert(balance)
+      println(result)
+      result.isBad mustEqual true
+    }
+
+    "fail to set spent > received" in {
+      pending // TODO: remove it when database checks are enabled
+      val address = DataHelper.createAddress("XmCEMpTo4r68N7hsmrYhNbfSqSVNJGb6qx")
+
+      val balance = Balance(address, received = BigDecimal(9), spent = BigDecimal(10))
+
+      val result = dataHandler.upsert(balance)
+      println(result)
+      result.isBad mustEqual true
+    }
+
+    "fail to set go negative on received" in {
+      pending // TODO: remove it when database checks are enabled
+      val address = DataHelper.createAddress("XauduFtKWMNZaPxqruayxp3S1kj9rvDxjN")
+      val initialBalance = Balance(address, received = BigDecimal(10))
+      val patch = Balance(address, spent = BigDecimal(11))
+
+      dataHandler.upsert(initialBalance)
+
+      val result = dataHandler.upsert(patch)
+      println(result)
+      result.isBad mustEqual true
+    }
+  }
+
+  private def combine(balances: Balance*): Balance = {
+    balances.reduce { (a, b) =>
+      Balance(a.address, a.received + b.received, a.spent + b.spent)
+    }
+  }
+}