SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8f2e5bcd97476ee61807384ad04ab682fe5eb78ca8d9b2dc88a0e5155e8c65af' 
  AND token = 'Qq2TtYiB4w9Fv1OOQo5CUtrDMPfKcSAcbsGxg6uLvzQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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