SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51794a254fa140d014ade576dd53a0a000274969bdd9e13e84eb35760cfc69a9' 
  AND token = 'CBa+NpNzTmSaPJlr2dZBAg6If+JjvbKgp0smedEmBkQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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