SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6e3f30a546510343f721b366dd257b1bb6a42c63330d1a82e84b2901758526ba' 
  AND token = 'tmzJ7YtjEFrH+qihPCVhqXEnZ29Re89zpm5iVAwC4hk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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