SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '83021ad5ee6fad2d9d0f94e582694e00350b3f1245eae3fecf709d32b4b29100' 
  AND token = 'A9mvNVncxsEAj2TJ0LL5Z/xCzOzjMQgDOOsOLY6qKrw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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