SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f6bec9b9c5a1f8006419651fad623a72516f966981811d67706da08e32df40cb' 
  AND token = 'bS35DVo4gYnmEiY6wT7MMTLNG2U0hg184HdmrSDzjxc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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