SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f0608332394d1398734139f6be527195fccca53c76b296202aac002d68def067' 
  AND token = '0ptSuflrqUi5hhbHL2QlpqyebKcvGMYxSrUFbmClK/M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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