SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f777bc1369c5ac64e5f70005d65a4d990610540b273b8529eff1a97d0d0b0d91' 
  AND token = '4EBgBsQb3eqGbkw6JDwCZuFv+dhnTRRz2s8qGWd4L9k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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