SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e543fbf193bda6f57a2aa8a49841be3693313a8dc906d70969b97d1ab5636a63' 
  AND token = '248m3ZGlOl0kQCgjx+WColzQER8ZXYtvMwXHFZEywTA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}