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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '875c68d8857ef6d21404fc1efbb15d6b67688ec517991b92456cf5aa2c0088dc' 
  AND token = 'R16XmrEcJPInHNHhxgKh7d1z47oOuD4HYm0id7nCIQg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00051

JSON explain

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