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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b294ddbc8a4be2ec2054f6512af07b2b1f0fd921cfa0d4ace5e6f0a68a60f8c8' 
  AND token = 'LUsscu/vmC3JWNmipDsBDdm83LeKKxi+rx+uwaD/QDc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00044

JSON explain

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