SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3397a836d7efd212d0769aaf6746c4f8502ada4fbacd47849bfe91e73df303a' 
  AND token = 'np34SQFBBdiE/j88uanWPHzJLwHgCUI1ywdxhvhzPyo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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