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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '939bafc3826501f51918e4ff494f50a83f46e92ce7ce144734805cfdc882cb74' 
  AND token = '4tcJEXb3oZnFd2AiTK/sUfPJSAKjwR5Zn+Oo/HWjD8w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00040

JSON explain

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