SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '17b090aeb1ce02a1f9f656a34470a4f9377af93dc7693b1dcc8dffbc4a0f18b9' 
  AND token = 'zK1Jz7R44czGrtVo0A0wYxgL0C+d+Tj7EbpjD5wwlBY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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