SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '420c0286459fe738667788c77a280e03eff4bf7267308a55b4c52bd3c5fab9f8' 
  AND token = 'JBqtgCo5zsSylFAPjUXlgm4BA2qxd9H+2Zi5hWuuFhQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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