SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '873e8ebb49179d7e5107f3d6dcc293162937e1c6ee8275d500f61c0fe202f1c9' 
  AND token = 'd6ArcHjIVN+7/nXuRPjJv0CcnuXgYYd/uZUv2aqoKGk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

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