SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a51f8d7d7270aeecb45e04127999aaf6d4ce10ae0018da24d52a9ba8cd00a097' 
  AND token = 'i/bf84cp/pr5/IE+VBtStKbYI3sLAJiuSI4Tb71XPao=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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