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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4bda0ab12af041f5b03759ca6c03b4b45c2b00eb3b15f74e0d755fa6e7a08dc3' 
  AND token = 'kqTcoOAjAeO55WUuBIp1OyqMn05sx2QYHRH5JZ76Zno=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}