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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4387f3fe9697f1fdb3ea0b77483307c0879e642666cb3ffab687973b6c8c5a39' 
  AND token = 'LSK+DENCbgwoOEpLWlZXMavBA+50DMjsXtdF6K2X7QM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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