SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4d9b21fa5a7c6a262014aa587cd384ebfd4f16b74dc68e45ad2a6e63c5973350' 
  AND token = 'QWzxjwGMVJjFtYyCUNrNvrg4pFWtl3tTTHc865gZeFI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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