SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ad6ff52a65568e22ec84a63c9eaddbe9997981831ab5e64a2d863877b502cd14' 
  AND token = '7UoBDAQhWiueCF3YKmb+RWWzyxiGJ1tOXd4hTKUBHgI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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