SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '78f7120cbe4844100de175497f7ae6b42fc19b3fb7d84334b76535d0fd082d7c' 
  AND token = 'TsUiMAN+gx4kvJ6CegK1/Lvgw5itTXX1VgQgUiLSgzA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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