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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a4df4f16417e46f4c2809a6804d7ea0c5d09b9b306de5fefb7665d93b9b8d8be' 
  AND token = 'Lb8ulGBFILvNKE0P3MGTUep1eb+TiwsoGn45xyrgCsQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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