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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21af1a88e0a6a5583504962c0f394da13e8d4d50deda9e2e4b06327144678690' 
  AND token = '/rZ6j11ZNexzzVUDA1ajy4knN35vfzWBI/BlpcR4MJI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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