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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9d8d8c522da298a99952e56f0c6d389d57c2e6b7be1c2ee1708a6155366a0873' 
  AND token = 'x86eJUYwHU7NCdWsgE14Bn19LxSC2XgMaDTu8LEg79E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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