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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '91912a1ca14d2bd810bbef0344981347824cab02b1d4aafe050a1caaa41ce38f' 
  AND token = 'HZhJZvVTAO22Q1PsR3OEdVC+xRxP+YvSHQMwVCZUasM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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