SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '400608b2df2d4c05a7d7c61f322963d3b919c955cefc54fac0f0812d5683e945' 
  AND token = 'r6tYzy3+XTbZ/UMpVTIR3wg2RH8NuMM1fAD+PUvGPTQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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