SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81ca607e94366db36f51aa892f453fe0fa7be1250fa6e91c26335928067bc901' 
  AND token = 'FnFz3g0NDoMbVFSts7MXKaAYD1+ULffSx22KEO6gpPQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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