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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd6b627b522ae5be995408a8127a8d56fe4b6eeb102c184702d234400612d391d' 
  AND token = '0qtqVeY30kx6twDBJzFveo/FTfEZCClMoJmNRG5Lttg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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