SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3a0997910a958513e42bfe7f75b755858a32dcc020660a2e7a2cdc2fbb52bd96' 
  AND token = '3jFoaSmtW4uaiy+BI5ZmRoxKRQQaurfMsWJZRbnejyk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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