SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a951ddd6699470569f955e0287f3de7bcd30c23e2f10ae56822f15363760fe9c' 
  AND token = 'Mz0JYvwPEdZV3LsooOQDKr+DVACtLIqyscABeiGbuzc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00048

JSON explain

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