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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '3715a4a7f48e2925c85c490e46fd21c511d1c8c924a4b990466513673081d9c4' 
  AND token = '1isa3YV6yrhzZfyP6RlBDyLdlaArl5F6BwDiIektOu8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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