SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6c3b7ff55b19024915825986db7265afc6a549e45a68c7e6348613d404d547e9' 
  AND token = 'JDjVQOFKtWg7o01P8GsVzRehRl1mbl1sphhIMOFq9pA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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