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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '891d47249d3cb68e0c553ff9fdb570f796db31f4228d2a1060c3a859f98ea2c9' 
  AND token = '6Q8HSYlM2hfEzOPPxd6v+bEYHOmIAIA+eRwGK2nNaiA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00051

JSON explain

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