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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4bf371a6651d964b7cdee2fb6b4b9bc493f05d6f266bab4b7ddc52842c81dd40' 
  AND token = '+B72oFMVUvZ7ZvyHcY17v1eO+M0Ri2dyjg24CMyKjGE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}