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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd390e281c952c95b350233406cc86bb93ab158322093d534bbe0256866c9db9c' 
  AND token = 'q/gUSHaSKxkvGe+hCC/3hjTkBUwmnMuUolPRQiMPIB4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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