SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '19aa8ef5bc87c09404199e8340acdbe7b8ea5343acf9fc9365a343878615bdda' 
  AND token = 'ZNQDHmnPwJ08GbF/YNjSqHGmWrc+hpTLjeAMMeD1HCo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00051

JSON explain

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