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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '49c5a4bf5c82f5ae80d1373d82c3d6fb4fe3c5e6c69330e97a0e63c2d697fd1b' 
  AND token = '51whOEBtDzMSPOnc40ijwVEYM+5jw7VD7U+7P/b70tA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}