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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6fa6b3b078f21f39d6bdfbbf58afeb44e898436ddaa5ba3ff00606d6af938aa4' 
  AND token = 'vXrWwNy/Hhve5N9WtyA0/Br3+nDpbmTVxiQuVKfDZz0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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