SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '923a3cee5c73d28a5b970f8132748a67a194d6fd0e4b0322187a3765df02d405' 
  AND token = '0r485jjg7/uzRAWQZR7bAM6XmK15N4bvb0llEZvDwCk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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