SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '939cedfbb7d5100d35498a071f028f8b2a90bba3e4214f71c5ce09535bec053d' 
  AND token = '+BVemhZJon2KWi5lI8EZltplPbOUhYVZnmWdtIGSZCY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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