SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e17be452a76b4ef2461b0201d8c138d7971702a6297e8799a44e6ae265033901' 
  AND token = 'uFLCuDnyYtoFwLDbgLQhdEhKC2lC2kzaUfzROJN4MEc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00053

JSON explain

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