SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6f376f28b7b9260c6db965712aaa4df46997e62d847e58ed6ed2b5267665051' 
  AND token = '4F84KBIzuI0yvXB/+smjsUCCfSjVdOJOHjHjr+EUV6I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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