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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '76a3e56c98f60f5801bbfc474f1c9455a1a0002b9f4aaef21a57d194f95feb44' 
  AND token = 'rRa9ZOOmsAJ5+eJt1mCGhyJ8owfljlQMRnwpf91MaQU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00047

JSON explain

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