SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4cb9fda81f36a2b385a372a2395d821686ec6a0cc317e2c81115343bf7f97210' 
  AND token = '1olNMcUVt9nuUwPxQF02v8RFsV38VfiPKhRAJNvxDwg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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