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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'fb50f0f320933a99de71b9f0bb1fc70e2dabb428e4873a2751e691ec816e25ff' 
  AND token = 'hHzZ5U9vI4ZMT8ZyE+0ZcoybuqkHH7f1DDrlosgmlwQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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