SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '399b740d5af33a095ede717153e83a361a3294dd5a7618cad808df99290e81e0' 
  AND token = 'oHBkmzyc/h1PUy2XXE4SxDWowqWkZ7K064xSBlbfeZg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00015

JSON explain

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