SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'af6b4a5e704e9a88a67c823afc85527d92636fda80e76f1d1dc920b9e387c4d1' 
  AND token = 'USk5HcI65S4MhpQgSYwIvUB1X3ZQTBaU9m5ZjHpG+oY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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