SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b81b6098bcd76dc642a1c3b2808ebc3fa0781f3d806c35bbbba46a157d30418c' 
  AND token = 'KBLtgHMEx9eSMEWH7z0W2KwrLmZi2eWGG/jGTGtlqgI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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