SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9d5f3535a1dd5331775e9908a53906c2c2bc4a1972dbb4bbe3b55ced77523551' 
  AND token = '6MGuGAYdoN/JmXDhnflrPFHXNdvbG6+QJKq447HK/WY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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