SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51b7089ea57f7044a02b2aed966870c607e4c4eb4b3316c3480eb32aa99eb182' 
  AND token = 'JmUOlW55tPWXurckE04IwEVQu4ParQc+B6HJCw54fbg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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