SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '396c4a60b750baf4f9bb851e4cb400862f856f5b56985fbfd51500bde01aa426' 
  AND token = 'LUgF3rgLzcUnCWH+SteQX4zxnjS+eCVVMl0FcyIwuFg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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