SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6768bd3de503d31e3de43c42341f4ebdada54250b993bacffcbea96142221f0c' 
  AND token = '8FFKT04RcuBoFF2nQGx1xajEDmAswAKBMDnhZ3iM70k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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