SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8a404a6f7c2b4b5d9e12f053daffe8962bc1ab9f7622577a48d08a9bd61af5dc' 
  AND token = 'LS5OPMqJQ/mUqN4i6NL0O1m6mf5euk4jxWNWMjwa3M8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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