SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cb43d54af73b75da7379f0074676fb6f7a3355be4a7ca2b195633f1491743713' 
  AND token = 'q8BYg9m+pS0w7ggqMVP5XKJWO+oCDGNiyoLNc8H9hWU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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