SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '54eaa8dac5869242fe273a35700841a297c3de0f97c9281e03808b902665fd28' 
  AND token = 'r3iQp5UcM6pyI9mITgMKP9lMHcPPmXPSuJTXe8joaMQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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