SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '56638b4bf8ec3867a7fb4d294da793a3f5254b3229e41641ca8eb1719da50390' 
  AND token = 'pD1WjhkKdCMhWpCoOKvFkuC+wqfYfJ+YYcf7IygQ5Rw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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