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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd50b51c2c17f95cce7ab9c5277c4d839645c4d379fa8099f9e50b56d5046c59b' 
  AND token = 'ATjVScnV+Il8pTMq4jG2H4OBkPXsm31qgt/0PkIfB2A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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