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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '519843aaceba0a1c76baae1c1cd7c77e51be6c06bb2ecc6253f03d31b626fd99' 
  AND token = 'MZm8SQOq1wht72g6pXb7+UV+j9VXP7EaJ2+QcCuusVE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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