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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '82c83a239936d85e0809e0171cf3a6ec6e58ccd1b5955e037d42a02a4e90dd61' 
  AND token = 'vKHSVuIcuyfgpRLgo+xG753RwfDyqcuhtuL+2B8UCQE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}