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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c7b7e7cc6d876067b80f2b0e279f821f3927c7760ca8eef7c48694deba6aab12' 
  AND token = 'pDwm+RiWSGAWM7MEULiZm21NbklBowFUYZL26P0CW8I=' 
  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"
    }
  }
}