SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '42d121203d3ffb73b433a0c007f17884e034b253353eb2c9360301946bc44d42' 
  AND token = 'UYzJUGSLBjVzB6rbxK7FGARQiNNLZrV3lMhbCIBiptg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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