SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '12f96db51cef969d3a608207780992ee31d5e90083847efa37e450a82907efc2' 
  AND token = 'CmHoj38aJTbAAzsg1lsVAoe5SSCyq7RUi+mxJhyz4bY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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