SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8c38313e85e78efc6f8b6af4e775d822c1d08dd6567751b7e6827939119a51b9' 
  AND token = 'ZaiZqph0O6pHwChjMgLPPCOgT5vn3urzYe9NSttLqUM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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