SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '36fe3fe84b9f143147c18977a10a32dadac4de4875ac0897085b4a6298520544' 
  AND token = '5rDUhbQHNuChgD72doyWUk1wDW7jqVoUAFv7fNAzPl4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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