SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '833081590bd79cf93a5abe2fd8f2b1dfdd4e5da1fc6ccb4481f60821ae1988f2' 
  AND token = '6gjBTbwrP0TkqAqaYMmtofQfBKw5XO3UAyEljjtk7/I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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