SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68b64a82bd5a8a1145dc70a1822c9e685392587443fafc537f9b06fc95f0d0bf' 
  AND token = '+lf3SzLxWt+fU4EOElJubKrZmQejvq51fohlJF0hlOQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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