SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9741989f3d792c4e6de01317c6104b73d128420aba697e20649e0e4a4c2b2780' 
  AND token = 'UfVCqF+LnsWbtnO0zo3TsvxEGVms0mUFmnTOfpdQUbM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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