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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8f144b7acba74c0558ebd2d8234b64e096907ed9fef845aa5c2973c87c0443e' 
  AND token = '6vYtC8g529feSueOJfPbOgXaADbn+tkQHYwypeT61Lk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00054

JSON explain

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