SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f35498ad916246765afe1f90d81d8f34b16171bee3b938330aa6a1cc2d4188d5' 
  AND token = 'awYSv0DKBYbpS1YEk99ArSMrYhMwhJgvvj7XY/qUSCA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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