SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3f904048b1a462289666c5c522856a3ae3eebc208b4af028403056f16539b570' 
  AND token = 'JUvLB/b2WPvOa7zAoIoTdVpguOLeP7ByrAqHTQJwRI8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}