SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '608ff43a38096927be29308d267cd89c28fb7808fa5a30de3c3301e10dedcaaa' 
  AND token = 'X2GzKhDil7ZLQ2LF2uhEDCqyCmJMqw+BzLrtrYnrRFQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00053

JSON explain

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