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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '50baae0a634d7ca3f3b0a4bab267a1f7a36d6d4bd3d075a9091b35d9593d19d5' 
  AND token = 'xynMrrZ4m53cwrTyj3JFMi7VaWYR5zg/e+hgJCX/cTE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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