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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9478891b9a1161c9880bc2b7a03aaaf8ed4c6886ff235a9e5db41a1cd36da550' 
  AND token = 'sl3Y8vBUT1BvHP8tvj4NmY4xQl1m1fE/f7EMBzfQeoI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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