SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7e951c6b9802f19f29b6015425017b612310e0a949434890897a716f0282c24f' 
  AND token = 'KmqHm8/TPpDYT6d/DPIi5UqgQ6BTyYYtR+/FfxnNfOI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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