SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '421cf0315982ebda5e965258a3288b8977de9f14af6151b1db9a9943f2f5d3a9' 
  AND token = 'CHdYzoecU/SnmMbiGRpgIhZbuGdlBUcLOVJklLqtZ8k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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