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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '789a175ac0f0e5e85d6596deb5f4a1ac2dfefeba8735a9217daf0dba978d786a' 
  AND token = '15BflOC+48uRZ1g8AL+vEeGZKVmdc4TMPtQSs7iJP3E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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