SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '588b998eef0208a2d8086430cd1f88b44b51482ac703e2e7a68e54ab3b70e640' 
  AND token = 'nlSY+iN78ub91XkPhD6rCcOPfyEhYMZnJgReUsasfYk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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