SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8b7583de7d0e4ea241a03e3964446340244869a4510da4864782fa9f812fe8a' 
  AND token = 'TSUhgM4xVYPmNjRJaoK1ypyBQiQRVK1pZbzVrYuKo/w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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