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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c1455d2e5c4a92bfd1fb3e056d12c8ea76f0fec2af12bde903d874ee5f25a38b' 
  AND token = 'bxaArasByBjnUNb7Aw1dQB9aB0w8Rpnl3vctnOgFxaE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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