SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a473ebc6b9d5d50f8f25c190d6d0a6758c494917b1e26086d03dea8d8f2bf4fa' 
  AND token = '57gYIUbYHy0CI5CjsCHHohGIU+Jgu5GmhzspoPhp6sg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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