SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3ec365a919e7d068f770dc19d27f0cbb9fc32844c6c1567bcbb4c4cd9d00ea8b' 
  AND token = 'JxzungClN4oL0xvmV1rt6PLjL8vuxo/wVTFnQzCo4js=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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