SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '261819d72ae7c633f443c1c36d25e6c4a7667ddaea00ac540d039db6542ff755' 
  AND token = 'CzKWVaNLwaSv1x32lUWbSMvaxgY8obTfxyf9xbflaYs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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