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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81d26a06c5f9ca62ed72bf7a4386ee3d1ec346e64d033f9605bf23d9fe5d3190' 
  AND token = 'm8RqhQTzBaZlfe2lraqrYrGI5V3kQ/yNWM83k9ySjPM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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