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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'ab4f126419825ba021c36439bbbb9ead9fa3ce5e0e9e53c680be641b201321b4' 
  AND token = '17DA7s8WPUTENGRMPEroozQTjNsDBBJfiGPBzl17DYk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00051

JSON explain

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