SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b5ea63b81b290aba66768321c09f84f728fa2ba31db378ca756353afd6515144' 
  AND token = 'smTFc7/V9NJiMGwlmycYG41Bba+qWDHEpj+OFP0waEo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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