SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '200f6a66fa4f7df3ab4acd541ca298c7691f0654db5eeb5af208af97478f430c' 
  AND token = 'DZ7dgvpAUUJGTH4uDNJobOkOJoxBI8Pj7y+AVDzv7AY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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