SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '938250e867bf5da32108f36bec255dfc3eb9064806375d70eb751babf64995d7' 
  AND token = 'XuFMHEmhCFhjTPt6c7clFjmA4CxfOPY5Y/LN4binfmY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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