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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'e4a46056cbbcc460aea42d841b572c314eec84da777ec3360b9c6b39bf0b6c7d' 
  AND token = 'L66RCEIRSVOduyDActg2C2mCTKcIxMYmItvDApt+nBM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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