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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81b8e470de1073df44b5c37468e648b802f52608016b764ad8698069ebe535c3' 
  AND token = '+qyhgeVQ4RzVQSHfGfEWeP/37ba/SCqM4ZaXmrHfJnQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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