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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c52c34ff940f51518075de0dbe49693f7e12043dd9fdc5241738b1569573b197' 
  AND token = 'pM6MrcxB/2rUVLIklqNv/pW370uuTxWPka+AQEN6kGM=' 
  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"
    }
  }
}