SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ce43b7f251583cb01597cc1465fa640f8f5f5337f98db4d55d887fc93773b832' 
  AND token = 'lL73ZwOJwqDVrT9DXE+msKxZPDqfBxmfe/HMgp30sbU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}