SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50b869ddb552ccacfe6e4a7df93d719e78bfd5b33a2d9bb1b35202eea1a99796' 
  AND token = '7rjZgCZmZYf+MJLaY5xErEQXmJSX3rGvn//Ez2+iVyc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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