SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6c5bcc747c1bcd3c523d338f28383c2b6a21b4021f41192023cfb666cbaf12e6' 
  AND token = '+djDvMZb+fquRNwZ9xtshZvRLveaAUO/8u4oABBkkp0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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