SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a993261557236417e63e32ac3d864d88e53cf67f613bfee583977faac8fee771' 
  AND token = '3NcQmQ2Y4tR/9u6OY1wQbRwQWYOzrBPn6vf09O46uM0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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