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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '878575f50adcd1ae386eb302cefe0ec15d7a2c969f8fdda90bc98d845286f899' 
  AND token = 'pUQoSDYCcC5mQcc1TyoNdqXGo1F8bdLibl7QN4MeD/s=' 
  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"
    }
  }
}