SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4a10d300e341ce62bce2cfa8770bf436df2ddaea4308cc1cc064de5e25220079' 
  AND token = 'Un+tDh8/oG6BzLli4KqqI2UtIgBaFsOHtPaSoFPuiC4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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