SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '251465879c86756181f9708630fc1c21984388231f8f95c2d6d02136ca7e79f0' 
  AND token = 'RWDoY9vtBgMsbtU1yADXTmX2+XvrXrprsY1T/jGPJzY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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