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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21975e541dbb18e78cb4cdb6da947380b843dca160979b75da0d6e500562b360' 
  AND token = 'TV4qe4mqpM2sYoo4mp9EF7tt5bV0TDuT/eWWbkxzd4c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00015

JSON explain

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