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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a935db7821f0f12ecf2236d60dbcb6942a9506a4d3da130640ab0cc9de2ecfa4' 
  AND token = 'l2XZJWUtVo6l9ZBlTACM7m6NEqgU2zBv7pRYjwi3cdQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00049

JSON explain

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