SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cf521af61e81c2d354740a76e8cdeb20a296c8472b1554388ecb6be42057251f' 
  AND token = 'UUXYrVgHCEnjvS9Unb0qncGfdSGb0+eIO1NjcqZJZ7s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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