SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5de90b1a3de0861fcd542973b6746dc54ce706e1feeb6562efdb49fb85506014' 
  AND token = 'nKrUphaRYPkND5bcslffILkMhqXPfMogw+rEz0SNzGk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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