SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '91c729c3cda6f018e983818382dfd114ed9fdb638c7049bf0d09a87d02700089' 
  AND token = 'S+5/EiAIRhhgTRSgya+aiGD00WxvNqk34xluDcbFizU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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