SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81cb8cb7aece27e861be63944b62f226648bd544d4a98b7375c60c67525f21c1' 
  AND token = 'UO+GfX2Brb4gsXv96995YfCihV+UyrxUDmSqh0LtNj8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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