SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a4c28d469201459425b101fa77114b2216d446003c4e1010a0af87c31545f403' 
  AND token = 'mOA5P9rXK9/QE9WOiDuNA6dPr42fcVgkYhGJvs5bjMA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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