SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = '15bd00f0bfd82db705b91b8d69d29fe5d5bc2981eb1e7882983b4ba7175f3a39' 
  AND token = 'Q0+RsqDMahIVYJJwBuWQNH/lq0iso7GlfSaO5KrQ+Yc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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