SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = 'b8eefd1a542d193cae9a401bbbb85c5609276be88957b2a0b07fd93e6e697099' 
  AND token = 'sc/gZVuJ3pe02ITZ5An1zIuHfaJvKiGz95P2UvRulog=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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