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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '0457f6e834cef7c5ce31c652a1d923980fa2e5bba757e33a52718dbb5fb5a257' 
  AND token = '9E7q32Kmea6TgmTvECD441AXx4Tu2DUeDv3out3+1NE=' 
  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"
    }
  }
}