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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3b8536425ca4bade6fa4e88268d70958026fe4390629bda7dea438ab5a5c79a2' 
  AND token = 'T4P2dum//ehC4EFoPrC2wKXaNMdHy2plP7+CFmk5TQM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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