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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c1351a56e29780a65d79f4486331bfccf54aa53eb68ed7f3013c4c6040e1537a' 
  AND token = 'Tkcl5ixs6b1vNTLuaFfFOnkv5slXTJyUE9PNyE77/Q8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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