SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '291a9cb016dac64b536f12d77f736b3a146296066e3b823daa898d7760253b56' 
  AND token = 'kHiNhNK+ocPiswIYMIxYj9o/COCPqsBgK6PKM4FpvaQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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