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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dc286dbdfb8a10b7dac73e70cc3e9a6321ec2b421e33435b66f6c61ae3c3c2ba' 
  AND token = 'mr8QvGGmFkmI+2f7u4/X/l//huK8HR5gWG4Ir2H/GV0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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