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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3b998826a113aa00e10ff4ecc2339cb1a1c7f08cec968a4be9aa1e9b8cd13a61' 
  AND token = 'xZR8JvBjR3twtDG43BdbBHjw7IBdFO+yiw4WUjhr/Oo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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