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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6c3b1c1dadc963dcc9452bd9e7cca6a2d210a27ecd7a3bbdfbbb6604da65d6a4' 
  AND token = 'SPMRStej1znBN8CepXc+tTd3N9LFwMF/MH69fZ6vFxQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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