SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21b8241ad189a9db9a1a2424c685fbd7daee61cc2a65c5266723a2d0eef796df' 
  AND token = 'GgbFUS4EudoeQ1ksmYc8CtzYallIKztjswXSkjb8LrI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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