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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fb351cfd98f73ada1a1c673e6ac957df74ed0da9720c748256df92aae4dac9aa' 
  AND token = '4PxxHFfYaPqZ3Yr5IIhpGfUOf4Mn6T2UUzziaCT7Cs0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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