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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6915b0ef7f56e2dc12f31177b3b33dff24c20598c1b1350398775e7751d8da9' 
  AND token = '2GS9QaQkKw7SyQetKo3/CZiejVIN4WPfBs+ZqHUub8U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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