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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd44a2c80e40055e0726d8779be8183e8c84d89040a755a5d1ce0945e3f838a1d' 
  AND token = 'McaMmml+JFqIoHaHPjoIkXdAQpc0MFqKIhiMb4hPFj4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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