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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '15b528ba3d4d973f0a789a1109ba2891fa7c8ee8c0bcaa2d7231b8bdb1aa35ba' 
  AND token = 'gMF89ofSsulIPf3BTRcHuUdP3nF4VYOmscsoPbMAdNI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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