SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4939bd1b350a2de7d461198034a881fd74b4e226aa22dd82d1cde17762feddb6' 
  AND token = '0zrVm/DZIaY2poKH3UE288MDAqNOZyJKdb6ckPVhKrE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}