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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e23f249d1f9f708c00b5fa1e8a9d42cbcf52aa2f0a57310c89d777bfaaf589a5' 
  AND token = 'rxaTmbu5venNZWyC7IrRc0q8kNlgI87vFu7Ev3wCyU0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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