SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b790843b1b2565106bb222300f378ee26c59eee32b563265c498eb9150ea6d4' 
  AND token = 'mDyWE4GkEkYPzaHHrnj2Y30laG0FrzmPqleRcDu/mBc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00013

JSON explain

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