SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '534ff56ae3292c394bfb01b5be0c1b14f21f0203825b4294acfc0d0645bee511' 
  AND token = '/ayXnfgpDWE3wWkFyWXKFJgI2KQ+thzk+sfoNt20WWU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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