SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6a862522c3b174d518efe3420a1b2a37405e7375580f824e063921ae86259386' 
  AND token = '0I4mOTCDYLRRWQwRyjWpo9WvqyuQpv7F6M+fQknaleU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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