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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6a43f3bfa2e8dbc345fb86e0124655029f0c548e1f84171ec95f1ddf61a81c1' 
  AND token = 't/kv9jMfr5TvUifoDreZ4VMFXCYx+sJxo/jHdyy38cg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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