SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fe971576f2a1288bb8dc8aff40558a41ce59fe76492ea3b10c3dfc2b1140839a' 
  AND token = 'YyCJFMpsbasGAnBai3AeadX2HUD5lC3wRzbakk6Glyg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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