SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '321a08494b3eedd075ef06996352b65437fa503fef517fd4e1bc6c003f82562d' 
  AND token = 'PXu0rJhCOUDHgJYqo0zCnQt8nEkStdqDxx6v/+Zf3vc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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