SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '492e749304487e0d0e835e74fa43dce62077346640f1fb3c1c8e8109581fbf21' 
  AND token = 'mB5YRLroKh6STSFjCxV1tORkImhCnG8vgnGxgLVOxzc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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