SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '83dbe037ec96f03826a3da05804f77b29b9b4aae022abbf02bc37d0b520ab956' 
  AND token = '6cwEhq1/whVK3uJ/LosowSfgUjvhjwjHgkvJs2fFjIg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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