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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51d436f2f8f528161e8899f9951dd155c03f4daf1ee02999db4d93ab861659a4' 
  AND token = 'J/1wind77xGKmJ3LKay6r9GuNxVdlFlQb1hbgj3BliQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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