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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6eaf87d5841892aa5b1887ddf935fc7b3294bfebee8f637132d9938d815dbad4' 
  AND token = 'r+w6hVQbFEb+ks/thIA4htGB6jGAvFycc/jO/t88Mgk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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