SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '840b6bf93285eb477837aed2febde645148fdcb0d9f8b603461d36fc5d97409d' 
  AND token = 'ROhOh4wj5a078Ivdu5qOT6g9AauxRsnpkgBHhhkkorg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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