SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '91296a96d4da0dd6183f68c6f05b7929cac8dd6c5e791f64124d67aa6220749b' 
  AND token = '3VqsrjrzApQEacBZqzePAjPyo3JYjFpwwOCHqq2snRI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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