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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c6407d5d71936d486ab1ff7e94ddec3074f6ae5374f1e15a4c85dd6f4e40ec28' 
  AND token = 'DfqbR3782ktjWEhQwOHbWqXwHz0o38hR2zRtE+37y0Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00052

JSON explain

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