SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cac8ac712b39b52b426e8305fccd1f4bb1f68c38f869a993d4957118060e2305' 
  AND token = 'YxRz24K/HVsLPuekvISgYVGdnVQfDdPX+HgqymRbuMU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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