SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f8d40754dd49491bd94849e6eed3fbc32afba6828c674d60678bb978923ba240' 
  AND token = 'bIXMmcViXbePA5kPih87ItTDQIhj3TYz5ufkFwe4sC8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00049

JSON explain

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