SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b76475109c412642d2727dc1734752f3ca9ede91eb46f511210753414889c3fd' 
  AND token = 'McSD1Fib4Idukqmny6eFQFiauS/p5FfEy/sPHqap9+0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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