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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21b7078e80b31df6b7fa6d6b34b1aa7d5099238aa2914fd743fc131e4a484e7a' 
  AND token = 'E3UrCq8Vobx7JNfcWh3B/xo7DlVZPx7ETTzPPn9MUUk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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