SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3f655a6929f8c63c527cfbe678449c515c9d5c67364b8453ae322127a19284a5' 
  AND token = 'zhGwUFiq/1+QsZ6C/Lze+ULFAT6eI0iY52zR7iQBTlY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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