SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fcfb81b2ee490481a93d0bf09dbd6629007cf63211a2962d9efdd037ebe321b4' 
  AND token = 'HoTQSOG4CEBXRc9Y3enWObf5+wXRuUWAh6rPzF6FCaQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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