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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6516e081a74b543ea46fdd8f7058bacfe347a8ffcb61a27efc139d3d296ce509' 
  AND token = '6krB4ExN2oDQ7InVZimLO8bPqohI7wKHlPhbalClrpQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00012

JSON explain

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